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ISDN Switch Off - A guide to your options.

BT ISDN / PSTN Swith-off...
A Guide To Your Options

By the end of 2026 traditional phone lines will be prepared to stop working in early 2027 and all calls will then be made over the Internet.


It’s the biggest and most important modernisation of the public telephone network ever, and your business needs to act very soon, if not already, to ensure a smooth transition. 

Thankfully, there is no need to worry about how it will work as we can help you get to where you need to be and ensure you don't miss any "Gotcha's" along the way. 


Despite what some may tell you, the good news is that there are four options to consider, all suitable for businesses ranging in size from as few as three employees to many thousands. All you have to do is to decide which option is the best fit for you, and we’ll help you do the rest. So if you have recently made investments in a new phone system or upgraded one, then that investment may not have been wasted.

Option 1: Adapt what you have

Extended life of your current phone system by connecting it to the Internet. This is simply done by adding hardware known as a VoIP gateway and a link known as a sip trunk, which uses your existing Internet connection. It's easy, affordable, and uses notice no difference – no new cables, no new handsets, and no training. Type of Organisation: Financial Services Call Volume: High No. of Employees / Phone Users: 30+ Best Fit: Option 1: Adapt What You Have IT Manager Mahmood says: "Ours is a high call rate operation with our advisors handling lots of calls every day so, for us, we wanted to maintain the same phones and PBX we've always had as our staff were very comfortable using them. Sangoma helped us move our communications system to SIP trunking using one of their gateways and we saved 30% pretty much overnight. The other brilliant thing is that because we didn't need to add new phones to anyone's desk, we didn't need to add more ethernet cables either, so our advisors could continue using WiFi on their laptops. We no longer pay BT line rental charges and apart from having the small router-sized Gateway next to our PBX, nothing has changed at all."

 Option 2: Upgrade what you have

Replace your installed on-premise system with the latest feature rich digital technology known as a unified communications platform. This can be installed on your site as hardware or software, fully under your control. All telephony now on the Internet, but also seamlessly aligned with your email, messaging and chat applications via easy to use, easily accessible user interface. Plus it can be all replicated on employees desktop computers, laptops and mobile devices for super convenience. Type of Organisation: Veterinary Practice Call Volume: Medium-High No. of Employees / Phone Users: 18 Best Fit: Option2: UpgradeWhat You Have Requirements: Multi-line call management (queuing, re-routing), Interactive Voice Response (IVR) Head Receptionist Sarah says: "Moving from analogue telephony to digital due to the switch-off in 2025 was only part of the picture for us. We knew that technology had the potential to help us provide our clients with an altogether better communication experience. Sangoma's experts sat down with us to really understand our business needs before recommending that we replace our existing system with another on-premise UC system and connect it via a SIP Trunk to place and receive calls. It instantly gave us the ability to manage calls more effectively. Reception staff are now able to see caller identity, transfer calls to extensions with just a couple of key strokes, place calls on hold, and automatically link call data to our appointments system. During busy periods, callers are automatically queued and receive information while they wait via automated messaging. There is also IVR functionality which enables callers to dial an extension number themselves. Al activity can be clearly seen on a nice big touchscreen and Sangoma are on hand to support if we have a query or an issue."

Option 3: Migrate to the cloud

Join the hundreds of millions of organisations worldwide by replacing your on-premise system with a powerful, cloud powered unified communications (UC) solution. All your calls, email, chat and messaging now via the Internet. Zero line rental; limitless ability to add the latest new features when you want. And pay monthly for just the services you use. Type of Organisation: Estate Agent Call Volume: Low No. of Employees / Phone Users: 8 Best Fit: Option3: Migrate t o the Cloud Requirements: Ability to continue to receive and make basic voice calls Owner Julia says: "I knew very little about the 2025/26 PSTN/ISDN switch of so, when a friend told me about it last year, Ipanicked. It turned out that I still had plenty of time to act so I did my research and decided a move to the cloud would work best for us. As well as voice calling, we get all of today's modern omnichannel communication functionality, such as email, messaging, chat, and social media, as well as a host of back-end data analytics, such as call recording and sentiment analysis, which helps with workflow design, improving customer experience, and agent training."

Option 4: Blend it all together

Mix options 1, 2 and 3 to suit your needs. For example, an on premise system at your head office, and a cloud base system serving your remote sites. Or connect a cloud based unified communications platform to an on premise VoIP Gateway or sip powered trunk system. Whatever the blend, enjoy the same seamless and integrated user experience. Type of Organisation: Courier Group Call Volume: High No. of Employees / Phone Users: 80 (12 UK Sites) Best Fit: Option4: Blend It All Together IT Director Andrzej says: "We wanted ot sweat the investment we had made only a few years ago ni our on-premise phone system but, at the same time, we are on a rapid expansion programme and opening satellite branches all the time. That meant, a hybrid mix of an on-premise and cloud-based system was a no brainer for us. Sangoma did all the heavy lifting - installing all of the Gateway and SIP hardware and software we needed at head office and ensuring all of the branches were on the new network. They also provided all of our branches with Sangoma P-Series desk phones, which have a stack of modern features and are pretty much bomb proof. They manufacturer them themselves so they are fuly guaranteed and supported, which is the kind of no nonsense approach we like. Ours is a fast-paced industry which relies on the increasing use of technology such as messaging apps and UC. The power of the cloud makes all that happen but having the best of both worlds feels like the perfect fit for us for now."

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