SIP trunking provides the connection between in-house PBX systems and the internet to allow you to make calls over the internet where you have a dedicated internet connection through broadband or leased line. SIP trunking gives businesses an alternative to ISDN lines which are being phased out by 2025 as well as offering lower costs and flexibility. Below we have explored what the leading providers offer.
The table below gives a quick price comparison of the top UK providers for SIP trunking.
| Company | Price from monthly |
|---|---|
| BT | £13 |
| TalkTalk | £120 |
| Virgin Media | Not stated |
| Zen | £30 |
| KCOM | Not stated |
| O2 | No monthly charge |
| Vodafone | Not stated |
| Stream Networks | £5.50 |
| Ai Networks | Not stated |
| hSo | Not stated |
| Telecoms World | £9.50 |
| Boxx Internet | Not stated |
| Andrews & Arnold | £1.20 |
| Cerberus Networks | Not stated |
| FluidOne | Not stated |
| Gradwell | £4 |
| Southern Communications | Not stated |
| Spitfire | £4 |
| Structured Communications | Not stated |
| Best 4 Business Communications | Not stated |
| Sipgate | £4.95 |
| Focus Group | £5.99 |
| Pioneer Global Services | Not stated |
| Talking Technology | Not stated |
* The facts and figures included here come from each company’s website and were accurate at the time of writing (January 2024) but may have since changed. Also, please keep in mind these may not be apples to apples comparisons as each provider offers different solutions. This guide should be used as a starting off point for more research on your part.
Below we profile each of the companies’ services and features in a bit more detail.
Note companies are ranked in no particular order and this no way indicates one solution is better than another.
1. BT
Some of the features and benefits of BT’s SIP trunking.
- BT Cloud Voice SIP connects phone systems to the internet
- Spend less on business calls
- More flexible services
- Greater control of your calls
- Prioritisation of your calls over the internet
- Built-in resilience
- Simple transfer
- Great for remote working
- Requires an internet connection with enough bandwidth which they can supply
- UK-based support and local engineers
2. TalkTalk
Some of the features and benefits of TalkTalk’s SIP trunking.
- Business phone networks delivered over the internet
- Greater flexibility
- Can offer financial savings on either PAYG or inclusive call bundles
- Highly resilient and offers multiple disaster recovery options
- Delivered over Ethernet data circuits
- Prioritises your calls over your data traffic
- Superior call quality
- Combine your voice and connectivity
- Scalable solutions from 1 trunk upwards
- 24/7 UK-based customer support
3. Virgin Media
Some of the features and benefits of Virgin Media’s SIP trunking.
- Uses data networks for voice communication
- Optimised secure data connection
- Single connection for data and voice
- Can plug straight into your existing phone system
- Maximise your data network
- Scalable solution
- Includes a range of call handling functionality
- Future-proofed solution
- Suited to medium to large businesses and multiple sites
- 24/7 customer support
4. Zen
Some of the features and benefits of Zen’s SIP trunking.
- Replaces or works alongside traditional analogue/ISDN lines
- Offers increased flexibility
- Opportunity to make cost savings
- Choice of geographical numbers
- Provides business continuity of automatic re-routing
- Delivers fraud protection
- Highly scalable solution to quickly add capacity
- Only pay for what you use
- Good for remote workers and multiple offices
- Only available to their connectivity customers
5. KCOM
Some of the features and benefits of KCOM’s SIP trunking.
- Highly flexible voice service
- Internet-based service
- Offers significantly lower costs than traditional ISDN lines
- Will recommend a solution to meet your needs
- Consistent quality
- Provides a business continuity solution
- Full scalability
- Seamless continuity
- Internet requirements vary depending on the bandwidth
- UK-based customer support
6. O2
Some of the features and benefits of O2’s SIP trunking.
- Flexible voice and data connectivity
- Can be easily adapted
- Resilient network
- Can make cost savings compared to ISDN
- Offer three simple packages
- PAYG and inclusive minute packages
- Scalable solutions
- Combine fixed lines, mobile and data
- Will help you select the best solution for your needs
- 24/7 customer support
7. Vodafone
Some of the features and benefits of Vodafone’s SIP trunking.
- Integrated service for voice and data
- Flexible solutions
- Offers tailored support
- Reliable service
- Offers value for money with cheaper solutions
- Secure IP connection
- Provides greater control
- Offers two options
- Caters for businesses of all sizes
- Claims to deliver superior customer service and support
8. Stream Networks
Some of the features and benefits of Stream Networks’ SIP trunking.
- Connecting businesses with voice solutions
- Reduced telephony costs up to 50%
- Unified communication systems
- Lower call rates and line rental savings
- Inclusive UK calls
- Fast setup
- Choice of 2 packages
- 12 or 36-month contract lengths
- Operate their own networks
- Has a minimum of 2 SIP trunks
9. Ai Networks
Some of the features and benefits of Ai Networks’ SIP trunking.
- Combined voice and data service
- Simple ISDN alternative
- Cost-effective and competitive call costs
- Connections available on a variety of line types including ADSL, EFM, FTTC leased line and dedicated fibre
- Can be combined with their CloudPBX system
- Offers a range of business-friendly features
- Number porting available
- Designed to carry a variety of media including voice, data and video
- Scalable solutions
- 24/7 monitoring and UK-based support teams
10. hSo
Some of the features and benefits of hSo’s SIP trunking.
- Offers complete integrated solutions
- Combines SIP with leased lines, WANs and internet access
- Resilient network
- Can make significant savings
- Offers a range of telephony options
- Prioritise calls over data traffic
- Seamless switchover
- Uses multiple SIP wholesalers to offer attractive call rates
- Scalable solutions
- 24/7 UK-based customer support
11. Telecoms World
Some of the features and benefits of Telecoms World’s SIP trunking.
- SIP trunking that is compatible with all leading PBX brands
- Reduces the costs of inbound and outbound calls
- Flexible and resilient network
- High-definition calls
- Free office to office calls
- They work with some of the leading PBX vendors
- Save up to 70% on line rental
- Scalable solutions
- Built-in business continuity
- Highly rated on Trustpilot
12. Boxx Internet
Some of the features and benefits of Boxx Internet’s SIP trunking.
- Offers onsite PBX and SIP
- Flexible alternative to ISDN
- Cost-effective solution
- Compatible with all leading PBX brands
- Better call quality through IP telephony
- Improved call handling
- Provides business continuity in the event of a disaster or emergency
- Future-ready for when ISDN lines get shutdown
- Call management solutions to arm your business with the tools you need
- Highly rated on Trustpilot
13. Andrews & Arnold
Some of the features and benefits of Andrews & Arnold’s SIP trunking.
- Flexible internet call solutions
- Inbound and outbound calls for larger companies
- Replaces ageing and expensive ISDN lines
- No limit on the number of channels
- Low-cost calls and monthly charges
- No cost for internal calls
- Low setup costs
- Easily scalable
- Not restricted to physical locations
- UK-based technical support teams
14. Cerberus Networks
Some of the features and benefits of Cerberus Network’s SIP trunking.
- Next-generation telecoms designed for businesses
- Cost-effective and competitive voice solutions
- Increased functionality and scalable
- No up-front investment on system hardware
- Choice of handsets
- Can use existing hardware if supported
- Offers number flexibility
- Quick and easy setup
- Provides business continuity
15. FluidOne
Some of the features and benefits of FluidOne’s SIP trunking.
- Connectivity solution for phones over the internet
- Great for controlling multimedia communication sessions
- Can be used for voice, video, instant messaging, virtual whiteboards, file and desktop
- Cost-effective with competitive tariffs
- Offers bundles of landline and mobile minutes
- Cheaper replacement for ISDN lines
- Tailored packages that are scalable
- Resilient with business continuity built-in
- Dedicated service delivery team that will get you set up in 2-4 weeks
- 24/7 customer support
16. Gradwell
Some of the features and benefits of Gradwell’s SIP trunking.
- Replaces the need for traditional phone lines
- Connects your existing PBX to the internet
- Added control and flexibility
- Secure service
- Can reduce your costs
- Scalable solution
- Competitive pricing
- Bespoke solutions which you can bundle in local, national and international numbers
- Can combine it with the connectivity services
- UK-based customer support
17. Southern Communications
Some of the features and benefits of Southern Communications’ SIP trunking.
- Offers a flexible SIP trunking solution
- Can offer a reduction in costs
- Suitable for a single user to a large call centre
- Scalable solutions
- Resilient with back-up and disaster recovery
- Combine voice and data connectivity
- Can use desk phones and mobile devices
- Requires a dedicated broadband or leased line
- Offers connectivity solutions to complement SIP trunks
- UK-based customer service
Southern Communications website
18. Spitfire
Some of the features and benefits of Spitfire’s SIP trunking.
- Install their own SIP trunks
- Lower rental and call costs
- Seamlessly works with most phone systems
- Provides assured call quality
- Highly scalable solution with fast deployment of extra capacity
- Resilient service
- Can be utilised for voice and data
- Allows you to consolidate line usage across sites
- Can include SIP gateways to increase compatibility
- Provides a dedicated account manager
19. Structured Communications
Some of the features and benefits of Structured Communications’ SIP trunking.
- Offers SIP trunks and channels
- Flexible phones lines for internet calls
- Lower costs for line rental and calls
- Increased flexibility to add channels and users
- Internal calls are free
- Portable with number flexibility
- HD quality calls
- Offers multi-level resilience
- Highly rated on Trustpilot
- 24/7 network monitoring
Structured Communications website
20. Best 4 Business Communications
Some of the features and benefits of Best 4 Business Communications’ SIP trunking.
- Internet service for voice and streaming media
- Bespoke solutions
- Lower line rental and call charges
- Flexible system
- Built-in disaster recovery
- Scalable solution with quick deployment
- Portable numbers
- Future-proofed for the ISDN switch off
- Can facilitate unified communications
- 24/7 support and monitoring
Best 4 Business Communications website
21. Sipgate
Some of the features and benefits of Sipgate’s SIP trunking.
- Connects VoIP PBX to the telephone network
- Premium voice quality
- No setup fees
- Highly flexible solution
- Competitive outbound call rates and no inbound call charges
- Can combine it with their hosted PBX system
- Helps combine services across locations
- Assists with disaster recovery
- Can be upgraded or downgraded at any time
- Provides 24/7 network monitoring
22. Focus Group
Some of the features and benefits of Focus Group’s SIP trunking.
- Cost-effective alternative to ISDN lines
- Increased flexibility
- Lower costs with free internal calls
- Compatible with all leading IP PBX brands
- Includes business continuity support
- Competitive call charges
- No connection fee or call connection costs
- Scale-up and down whenever you need to
- Suitable for businesses of all sizes
- Award-winning provider
23. Pioneer Global Services
Some of the features and benefits of Pioneer Global Services’ SIP trunking.
- Offers the benefits and advantages of VoIP services
- Utilises your existing telecoms setup
- Replaces ageing ISDN
- More affordable call charges than traditional phone lines
- Incorporates home workers
- Number porting
- Scalable solution
- No area restrictions on numbers
- No expensive call forwarding services
- UK-based support
Pioneer Global Services website
24. Talking Technology
Some of the features and benefits of Talking Technology’s SIP trunking.
- Flexible alternative to ISDN lines
- Lower cost solution
- Quicker installation
- Robust business continuity built-in
- Free internal calls
- Offers a host of features
- Scale-up and down when needed
- Compatible with Skype for Business
- They work with a range of PBX vendors
- Caters for a range of business sizes
How Does Sip Trunking Work?
Session Initiation Protocol (SIP) trunking is a technology that allows organizations to make and receive voice and multimedia communications over the internet, enabling them to connect their private branch exchange (PBX) phone system to the public switched telephone network (PSTN) or other SIP-based systems.
Here’s how SIP trunking works:
Establishing a Connection: The process begins with your organization’s PBX or communication system (e.g., VoIP phone system) connecting to your Internet Telephony Service Provider (ITSP) or SIP trunk provider over an internet connection. This connection is typically made via a dedicated line or a virtual connection.
Session Initiation: When someone in your organization makes an outbound call, the PBX sends a SIP request to the SIP trunk provider’s servers. This request includes information about the call, such as the destination phone number.
Routing and Authentication: The SIP trunk provider processes the request and authenticates it to ensure it’s coming from a legitimate source. Once authenticated, the provider routes the call based on the destination phone number. If it’s an international call, the provider may also apply specific routing rules and rates.
Media Exchange: After routing the call, the SIP trunk provider establishes a communication channel between your organization and the destination phone number. This channel is used for transmitting voice or multimedia data. SIP facilitates the negotiation of the media type and codecs for the call.
Call Termination: The call is connected to the recipient’s phone, and the conversation can take place. The SIP trunk provider manages the call throughout its duration.
Incoming Calls: When someone calls your organization, the SIP trunk provider receives the incoming call, identifies the appropriate destination within your organization (based on the DID – Direct Inward Dialing number), and routes the call to your PBX.
Redundancy and Failover: Many SIP trunk providers offer redundancy and failover options. This means that if one connection or server fails, calls can be rerouted through an alternative path to ensure business continuity.
Quality of Service (QoS) and Security: SIP trunk providers typically offer quality of service options and security measures to ensure that calls are clear and secure.
Billing and Reporting: SIP trunk providers bill you based on the usage of their service, often charging per minute or with a flat fee. They also provide reporting and analytics so you can monitor your call usage and costs.
Scaling and Flexibility: SIP trunking allows for easy scalability. You can adjust the number of channels or lines as your organization’s communication needs change. This flexibility is one of the key benefits of SIP trunking.
SIP Trunking vs VOIP: What’s The Difference?
SIP trunking and VoIP (Voice over Internet Protocol) are related but distinct technologies that are often used in conjunction. They both involve transmitting voice and multimedia communication over the internet, but they serve different purposes and are used in different contexts. Here’s a comparison of the two:
SIP Trunking:
Purpose: SIP trunking is primarily used for connecting an organization’s private branch exchange (PBX) or phone system to the public switched telephone network (PSTN) or another SIP-based system. It’s used for making and receiving external calls to and from the organization.
Connection Type: SIP trunking is typically used for outbound and inbound voice calls, but it can also handle multimedia communication. It is often associated with traditional phone systems and is used to bridge the gap between these systems and the internet.
Hardware: SIP trunking may require specialized hardware at the organization’s premises, such as an IP PBX, session border controller (SBC), or gateway, to facilitate the connection with the SIP trunk provider.
Cost Structure: SIP trunking is often billed based on the number of channels or concurrent calls a business needs, offering flexibility in scaling the service according to demand.
Integration: It’s a useful technology for businesses that want to leverage their existing phone systems while also taking advantage of the benefits of VoIP.
VoIP (Voice over Internet Protocol):
Purpose: VoIP is a broader technology used for transmitting voice and multimedia communication over the internet or an IP network. It can be used for both internal (within the organization) and external (outside the organization) communication.
Connection Type: VoIP encompasses various communication methods, including voice calls, video calls, messaging, and more. It’s used for real-time communication within and outside the organization.
Hardware: VoIP can be implemented using softphones on computers, IP phones, or mobile apps, and does not require a traditional PBX. Cloud-based VoIP services often eliminate the need for on-premises hardware.
Cost Structure: VoIP services are typically subscription-based, with businesses paying a fixed monthly fee for each user or extension. Some services offer unlimited calling.
Integration: VoIP is often used as a standalone solution or as part of a unified communications platform, which may include features like video conferencing, instant messaging, and email integration.
Hosted PBX vs SIP Trunking: Which Is Better?
The choice between hosted PBX (Private Branch Exchange) and SIP trunking depends on your organization’s specific needs, infrastructure, and priorities. Both solutions have their advantages and may be better suited to different scenarios.
Here’s a comparison to help you decide which one might be a better fit for your business:
Hosted PBX (Cloud-Based Phone System):
- Hosted in the cloud by a service provider.
- No need for on-premises PBX hardware.
- Managed and maintained by the service provider.
- Typically a subscription-based service.
Advantages:
- Minimal upfront capital expenditure as there’s no need for PBX equipment.
- Scalability: Easy to add or remove extensions and features as needed.
- Simplified maintenance and updates, as it’s managed by the provider.
- Remote and mobile work support.
- Often includes a range of features like voicemail, call forwarding, auto-attendant, and unified communications.
Consider If:
- You want to eliminate the burden of managing and maintaining on-premises equipment.
- Your organization is small or growing rapidly and needs a scalable solution.
- You have a distributed or remote workforce.
- You prefer predictable monthly subscription costs.
SIP Trunking:
- Connects your on-premises PBX or phone system to the public switched telephone network (PSTN) using SIP technology.
- Requires on-site equipment (PBX) or SIP-compatible infrastructure.
- Billed based on the number of concurrent call paths or channels.
Advantages:
- Integration with existing on-premises phone systems, preserving prior investments.
- More control over your hardware and infrastructure.
- May be cost-effective for businesses with large call volumes.
- Can be used with multiple communication methods, including voice and multimedia.
Consider If:
- You have a significant investment in on-premises PBX equipment that you want to leverage.
- Your business requires customizations or specialized features not readily available in hosted PBX solutions.
- You need high call volume capacity.
- Your organization has the IT resources and expertise to manage on-site equipment.