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One Voice SIP Trunk UK

Put your calls in the cloud with this phone system that lets you do more while saving money.

Get in touch

Thinking of joining us?

0800 345 7984

09:00 - 18:00 | Monday to Friday

Existing customers

0800 085 5957

09:00 - 18:00 | Monday to Friday

Existing customers

If we’re already working with you, please get in touch with your account team or account manager. We’re happy to talk through the technology solutions we can offer to support your business.

Chat with a UK-based sales specialist

09:00 - 17:00 | Monday - Friday

Existing customers

If we’re already working with you, please get in touch with your account team or account manager. We’re happy to talk through the technology solutions we can offer to support your business.

New sales enquiry

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Set your phone system free

Take the first step towards unified communications

The cloud is calling. One Voice SIP Trunk UK offers an IP alternative to traditional voice services. It helps you take control of your costs and work more efficiently. While keeping up with growing business demands and embracing new collaboration tools. All running on a network you can rely on.

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Bring all your communications together

This SIP phone system links up all your systems. So you can consolidate your IT and communications infrastructure, streamlining your costs and simplifying how you manage it all. You can even keep your existing hardware, unlike many hosted solutions.

One Voice UK SIP Trunk is flexible. So it can connect your current PBX to our UK data networks, such as MPLS, that will join up all of your sites together with remote workers.  While laying the foundations for future cloud transformation.

Discover the benefits of One Voice SIP Trunk UK

All-in-one communications

As well as making voice calls over the internet, your people can work better together from anywhere, using instant messaging conferencing. 

Cut costs by 30%

With our centralised connectivity, you can eliminate expensive interfaces and reduce the number of channels you need to handle your traffic.

Resilient rerouting

If something goes wrong, calls can be diverted. Our SIP solution can do this automatically or you can manage it yourself through an online portal.

Flex for what's next

Rather than pay for peak capacity all year round, you can scale your system up and down depending on how busy you are.

Choose the right amount of channels for your business


Designed for the average desk phone user, it has enough throughput to handle everyday peaks and troughs in traffic.


Ideal for call centres, this premium package supports near-constant use with guaranteed 1:1 network contention for the highest quality communication.

Helping Kingston University stay one step ahead

The higher education sector is now as commercially driven as big business. As government funding has declined, it’s now more important than ever that Kingston University attract as many students as possible. One Voice SIP Trunk UK gives them the flexible call capacity to keep up with the demand of the busy summer recruitment drives while keeping costs down.

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“The BT solution ticked all the boxes and would give us everything we needed and more.”

Simon Harrison

Chief Information Officer, Kingston University.

Read our case study with Kingston University

The challenge: Old technology foiling new students

Kingston University’s old analogue phone system couldn’t cope with a surge in calls coming through during its recruitment drives. The system was also increasingly expensive to maintain and run, and there was no back-up plan for if anything went wrong.

‘The number of calls we get shoots up as soon as the A-level results come out’, said Simon Harrison, Kingston’s Chief Information Officer. ‘As with most universities, we take a number of students through Clearing, with most being offered places in the first couple of days  – so if the phones aren’t working, we stand to lose potential students. We simply couldn’t run the risk of losing the possible income’.

We already provided the university’s voice services and IP phone system, so Simon discussed ways round the Clearing problem with us.

The solution: Transforming how people work

We recommended BT One Voice SIP Trunk UK. The clever thing with this solution is the university uses its IP connection for calls rather than the traditional phone lines, helping to save on call charges.

To remove the risk of the phone system going down, we also installed a BT IP Connect Wide Area Network. As the access circuits are in different locations, at two of the university’s data centres, the phone lines are always available. If anything goes wrong with one circuit, (cable damage during building works, for example) calls automatically re-route to the other one. So for the university, it’s always business as usual.

And because the network uses multiprotocol layer switching (MPLS) technology to prioritise voice calls, callers can always get through to the university. What’s more, Simon can effectively switch SIP channels on and off, matching call capacity to demand so when things get busy they can expand the system to take more calls. So Kingston University is always ready for anything.