Award-winning SIP Trunks

Connect your PBX to the PSTN in minutes with Gradwell's trusted SIP Trunks.​
Trusted by over 8,000 businesses
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What Are SIP Trunks And How Do They Work?

Designed to replace traditional phone lines, SIP Trunks use broadband internet connections to connect your business phone system (PBX) to the traditional phone network (PSTN) without needing to replace your existing hardware.

With the PSTN network due to be switched off by 2025, now is an ideal time to experience the benefits of connecting your business phone system to the internet.

Benefits of SIP Trunks

Cost effective

Lower installation fees and monthly costs, including DID provisioning and call charges for both national and international numbers.

Improved service levels

Ensure that customers can reach you, wherever they (and you) are at a lower cost and via a quality connection.


Change location, expand into new markets and forward calls at a moment’s notice without any business disruption.

Easy management

Instantly provision additional resource as needed, on a permanent or temporary basis.

Flexible numbering

Regardless of physical location – even if this changes –present local, non-geographical or international numbers as needed.

Why Gradwell?

We are the UK’s SIP pioneers and we take pride in the resilience of our network. We have a team of over 20 developers who are constantly evolving and advancing our technologies. That’s why we’re trusted by hundreds of organisations for business-critical SIP services. See what else makes Gradwell stand out from the crowd below:

Our own network
We operate and optimise our own network, security and systems directly from our HQ.
Cloud based
All of our SIP Trunks operate in the cloud.
Resilient and secure
We are ISO 27001 certified and our Network Operations Centre monitors our systems at all times.
Trusted by thousands
Thousands of UK businesses rely on us for secure and cost effective SIP Trunks every single day.
Recommended by the best
We are one of only a handful of suppliers to have 3CX preferred status, with a native 3CX integration and set-up
Easy management
Manage your SIP channels through our easy-to-use centralised portal

Specialist SIP services

We offer a wide range of bespoke SIP products to meet your specific requirements.


Use Microsoft Teams as your business phone system. Direct Routing is the process of connecting Microsoft Teams to the traditional phone network, or PSTN. It is an increasingly popular way to turn Teams from a powerful internal communications tool to a full-scale unified communications platform.

Learn more

We are a market-leading 3CX solutions provider – from onboarding and setup to support and maintenance, we help businesses feel secure when purchasing the 3CX system. Our end-to-end packages all include UK-based support, SIP trunks, connectivity and hardware. Deployed in a highly resilient cloud to guarantee service levels – not included in most suppliers’ standard offering.

Learn more

We have designed our own high-volume SIP Trunks specifically for customers needing high call-per-second and high channel capacity. Integrating directly with your existing PBX, our high-volume SIP Trunks allows you to take advantage of the cloud-based solutions, without replacing your existing equipment.

Learn more

“Gradwell’s SIP Trunks are critical infrastructure and the backbone of our product. It’s the only way we can do what we’re doing, at the price level we need it to be."

Sam Gillingham
Marketing & Operations Director, VoiceIQ


We offer some of the most competitive rates available.


One channel included
£ 4
Per month, per channel
  • Calls from 1.5p/min
  • Unlimited inbound calls


One channel included
£ 8
Per month, per channel
  • 3,000 UK landline minutes
  • 1,000 UK mobile minutes


One channel included
£ POA Per month, per channel
  • A range of international minutes

Not sure how many channels you need? Click the button above to chat with us.

All prices quoted are minimum possible. All installations require a £25 setup fee. View our full tariffs here. International minutes available at extra cost.

Industry recognition and accreditations
Comms National Awards
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Comms Council UK
Fast 50
Sparkies Awards
BSI 27001
Best Companies

Trusted by our customers

We pride ourselves on finding solutions that help our customers, whatever their expertise.

We work with in-house IT functions with exacting requirements, to business owners and office managers who are new to telephony and communications.

Join thousands of businesses

We’ve helped organisations from across the UK take advantage of cloud-based communications tools. Can we help you?


High-volume SIP Trunks run on a separate dedicated platform built for high volumes of traffic and CAPS. This allows you to use the volumes you want without any issues.

 Not at all! You can have as many as you like from as many locations as you want.

Porting numbers can take up to two weeks depending on how many you have! We will request it as soon as possible and inform you when your number has been ported.

Built in the UK, we have a team of over 20 developers who are constantly evolving and advancing our technologies. With a range of packages to suit your business needs, you can tailor our products and services to suit your business needs and demands.

Simply give our team a call on 01225 800800 and they can set up extra users in a matter of minutes.

Gradwell has a wide range of connectivity options available that are suitable for running our SIP trunking services over. In just a few questions, our team will be able to advise which connectivity option is suitable for your business.