BT's PSTN switch-off, the programme to retire traditional copper telephone lines, reaches its deadline in January 2027. If your phone system still runs on traditional lines, you need a plan. Most businesses I speak to either know this and haven't acted, or genuinely haven't heard of it yet. Either way, the timeline is real.
VoIP (Voice over Internet Protocol) routes calls over your internet connection rather than a dedicated phone line. Done well, the call quality is identical to a traditional line. Done badly, you get choppy audio and dropped calls and staff who route around the new system by using their mobiles.
The cost and flexibility case is genuine
Hosted VoIP from providers like 8x8, RingCentral, Gamma, or Microsoft Teams Phone typically costs £10-20 per user per month, including the number, calling plan, and features. For businesses maintaining an ageing on-premise PBX with a separate support contract, the savings are usually immediate.
The flexibility argument is also real, not marketing. Staff can receive calls on a desk phone, laptop, or mobile app, all appearing on the same extension. Someone working from home is indistinguishable from someone in the office as far as callers are concerned. Call recording, voicemail to email, call analytics, and auto-attendant are typically included at no extra cost in modern platforms.
The three things that go wrong
Internet dependency is the obvious one. Your phones depend on your internet connection: if it goes down, so do calls. The solution is a failover connection or a configured mobile fallback. This is manageable, but it has to be planned before the migration, not after the first outage.
Network quality is less obvious but bites more often. Voice calls are sensitive to latency and jitter in a way that email and file downloads aren't. A network that works fine for general use can still produce choppy calls if it's not configured to prioritise voice traffic. QoS (Quality of Service) settings on your router and switches need to be set correctly. This is a five-minute configuration task, but it's regularly skipped.
Power dependency catches people off guard. Traditional phone lines carry their own power, so your phone works even in a power cut. VoIP phones need mains power and a working router. A UPS (uninterruptible power supply) on your router and switch keeps telephony running through short outages. Budget around £80-150 for a suitable unit.
How to choose a provider
For Microsoft 365 businesses, Teams Phone deserves serious consideration. If your team is already in Teams all day, integrating calling removes the need for a separate phone app entirely. The per-user licensing (around £8-12 per user per month on top of your existing 365 licence) adds up at scale, but the consolidation is operationally straightforward.
For other businesses, look for a provider with UK-based support, clear SLAs, and a track record you can verify. Ask specifically about their number porting process (transferring your existing numbers to the new provider) and insist on a parallel running period before you cancel your old service.