The UK’s traditional telephone network — the PSTN (Public Switched Telephone Network) and ISDN — is being switched off. Openreach is retiring the old copper network and moving every line over to digital, internet-based calling. Any service that still depends on an analogue or ISDN line will need to migrate before the network goes dark, and the current industry target for full switch-off is early 2027. That sounds far away, but for a busy business it really isn’t — and the lines aren’t waiting around either, with new analogue and ISDN orders already withdrawn across most of the country.
If your phones still run over copper, this is one of the most important infrastructure changes your business will make this decade. The good news: handled properly, it’s an upgrade, not a headache.
What the switch-off actually means
For decades, business calls travelled over a dedicated copper phone network. From early 2027, that network stops carrying calls altogether. In its place, telephony runs over your internet connection using VoIP (Voice over Internet Protocol) — the same technology behind hosted phone systems and Microsoft Teams calling. Calls become just another piece of data on your broadband or leased line, which is exactly why the new model is more flexible and usually cheaper to run.
The shift has been deliberately phased. A pause in 2024 addressed concerns about vulnerable users and critical devices that quietly rely on the old lines, but that was a timeline adjustment, not a cancellation. The copper network is still going away.
It’s not just your office phones
The biggest risk with the PSTN switch-off is the things people forget are connected to a phone line. Anything running over analogue can be affected, including:
- Office phone systems and ISDN lines
- Card payment terminals
- Door entry and intercom systems
- Alarm and CCTV signalling
- Lift emergency phones
- Fax lines, franking machines and some legacy monitoring kit
Each of these needs identifying and either migrating to a digital equivalent or replacing. A lift emergency line that stops working is not something you want to discover after the switch-off date.
Why migrating early is the smart move
Leaving it late is where businesses get caught out. Rushed migrations mean number-porting delays, downtime and last-minute costs. Plan ahead and the change is smooth — and you get to treat it as a genuine modernisation rather than a forced scramble. Moving to VoIP typically brings:
- Lower running costs — fewer line rentals and cheaper calls.
- Flexibility — staff can take calls anywhere, on a handset, laptop or mobile.
- Easier management — add or remove users in minutes, with no engineer visit.
- Better resilience — calls can be rerouted instantly if a site or line goes down.
- One joined-up system — calls, voicemail, chat and meetings together, especially with Microsoft Teams calling.
What to do now
You don’t need to solve everything at once — you need a plan. We’d suggest three steps:
- Audit every service in your business that uses a phone line, not just the obvious handsets. Build a simple list of lines, what they do, and which are critical.
- Plan your migration to VoIP or Microsoft Teams Phone, including porting your existing numbers so customers never notice the change.
- Upgrade in a controlled, staged way — testing as you go — so you switch with confidence and zero surprises.
Getting the underlying connectivity right matters too: VoIP is only as good as the broadband or leased line beneath it, so it’s worth checking your connection can comfortably carry your call volumes.
How Lumen MSP can help
We migrate businesses off the old network every week, and we handle the whole journey — auditing your lines, recommending the right platform (hosted VoIP or Microsoft Teams calling), porting your numbers, and supporting your team through the change. As a managed service provider we look after the connectivity, the phone system and the support under one roof, so there’s no finger-pointing between suppliers when you need help.
The earlier you start, the smoother and cheaper the switch. Talk to Lumen MSP about your PSTN migration, explore building a modern phone system, or call us on 0333 335 0170 for a no-pressure chat about the best path for your business.