The flexible, scalable SIP trunking provider you've been searching for.

Secure a cost advantage and ensure reliable, high-quality business communications with our enterprise-grade SIP infrastructure.

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SIP trunking products for businesses of all sizes


3CX tested and certified SIP trunks.

Direct Routing

Use Microsoft Teams as your business phone system.

High volume

Best-in-class contact centre functionality. 

3CX SIP trunking

True PBX flexibility. Powered by Gradwell.

We are a market-leading 3CX Titanium Partner and solutions provider. From onboarding and setup to support and maintenance, we enable businesses to get more out of the 3CX system. This includes our 3CX certified SIP trunk services, providing reliable SIP at competitive prices to maximise your investment.

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3CX preferred SIP trunking supplier

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Set up and configure in minutes with pre-built 3CX template

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Secure and reliable

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Direct Routing

Use Microsoft Teams as your business phone system.

Direct routing is the process of using SIP trunks to connect Microsoft Teams to the traditional phone network (PSTN). With Gradwell’s SIP, you can turn Teams from a powerful internal communication tool to a full-scale unified communications platform.

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Low installation fees and monthly costs

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Flexible numbering and porting services

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Add advanced telephony features with Wave Teams+

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High-volume SIP

SIP trunks for contact centres.

We have designed our own high-volume SIP trunks specifically for customers needing high call-per-second and high channel capacity. With unlimited inbound SIP, expect no delays in call connection, even at peak times. Integrating directly with your existing PBX, our high-volume SIP Trunks allow you to take advantage of cloud-based solutions, without replacing your existing equipment.

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Pay as you go and blended minute bundle options available

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No delays in call connection, even at peak times

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Performance tested with all major PBX vendors

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The smart way to enable communication with the leading UK SIP trunking provider

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“Gradwell were by far the best value for money quote that we received. The Gradwell pricing structure is just phenomenal – such a massive difference from some other providers, and together with their exceptional service levels, it really was a no-brainer.”

Chris Goodchild,

General Manager

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“All of our colleagues are now making use of Teams with Gradwell’s Direct Routing as a Service solution. We now have a highly available modern unified communications and telephony platform which requires little input from ICT technical staff.”

Jason Hanger,

Cloud Solutions Engineer

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“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,

Operations Director

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Award-winning service from the SIP trunking pioneers

Our own network

We operate and own our own infrastructure and SIP network. This gives us control over our service, security, scalability and enables us to offer highly competitive pricing.

Trusted by thousands

We support thousands of UK businesses, who rely on us for secure, reliable, and cost-effective SIP trunks to manage their teams.

Resilient and secure

We are ISO 27001:2013 certified and our Network Operations Centre monitors our systems 24/7.


Our experts answer your most common questions about our UK SIP trunking services.

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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.

What makes Gradwell SIP different?

Built in the UK, we have a team of over 25 developers who are constantly evolving and advancing our SIP infrastructure. Our SIP trunks are performance tested with all major PBX vendors, deployed in a highly resilient cloud environment (AWS) across multiple carriers and come with a range of flexible packages including PAYG and bundle options.

How does high volume SIP differ from normal SIP trunks?

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, regardless of fluctuations in demand and usage.

How long will porting my number take?

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.

I'm not sure if I have a good enough internet connection for SIP.

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.

Why Gradwell?

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Expert support

Receive as much or as little help as you need from our dedicated UK support team – 24/7/365 – and only pay for what you need.

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Born in the cloud

We’ve always engineered our solutions in the cloud, benefitting from decades of experience plus learning and responding to the market.

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Secure & compliant

Enjoy total peace of mind thanks to our ISO 27001:2013 certification, Microsoft Gold Partner and 3CX Titanium Partner statuses.