It's the third dropped call before lunch. A customer rings back to say they got cut off halfway through, again. Someone on your team is working from home, and the office number just doesn't reach them. None of it is a crisis on its own, but a customer who can't get through twice doesn't always ring a third time.
Here's the bit that changes the timeline. On 31 January 2027, Openreach switches off the old copper phone network for good. PSTN, ISDN, all of it. There's no extension. If your business still runs on analogue or ISDN lines, you have to move, and the sooner you understand your options, the less this feels like a scramble.
This guide explains what VoIP actually is, how it compares to your current setup, what to look for in a business phone system, how VoIP providers stack up against each other, whether hosted or on-premise suits you better, and what it really costs. Whether you call it a business telephone system, an office phone system, or just "the phones," the same decision applies before 2027. Plain English throughout. No jargon you have to decode, no scare tactics, just what you need to make the call.
PSTN stands for the Public Switched Telephone Network, the copper wiring that's carried UK phone calls since the Victorian era. ISDN is the digital layer many businesses added on top of it in the 90s and 2000s. Openreach is retiring both. Every business still relying on them has to move to an internet-based phone service before the switch flips.
The scale of what's left is still significant. In February 2026, Openreach reported roughly 2.8 million lines still on the PSTN network, more than half a million of them serving business premises. By July 2026 that had fallen to around 1.5 million lines, including roughly 350,000 business premises. Progress, but hundreds of thousands of businesses are still exposed with less than a year on the clock.
Waiting isn't free, either. Openreach's wholesale line rental has been rising in stages through 2026: up from £10.65 to £12.78 a month plus VAT on 1 April, then a further 40% rise on 1 July, and another on 1 October, taking rental to roughly double what it cost in 2025. A 20-line business paying around £213 a month for line rental in March 2026 is looking at roughly £501 a month by October, for a service that's being switched off anyway.
It's not just phones, either. Alarm systems, card machines, and lift emergency lines often run on the same copper network. Openreach flagged more than 12,000 lift lines and around 500 CCTV network connections still needing an upgrade earlier this year. Check what else in the building runs on the old lines before you assume it's only the phones on your desk.
And the earlier you start, the calmer it is. Number porting, the process of moving your existing phone number to a new service, typically takes 10 to 15 working days. Leave it until December 2026 and you're competing with every other business trying to do the same thing at once, against fixed installer availability.
Not a plan:
A phone call in the next few months is.
Picture your voice getting chopped into small packets of data, sent down your internet connection instead of a copper line, and reassembled as sound on the other end, fast enough that neither side notices it happened. That's VoIP, short for Voice over Internet Protocol, and it's really all you need to know about how it works.
You can take the call on a proper desk phone, an app on your laptop (a "softphone"), or your mobile, all using the same business number.
Your provider might describe this as "synergising your unified communications estate." We'd rather just say: your phones start working over the internet instead of a phone line, and your number follows you wherever you're logged in.
Worth being straight about both sides here, because most guides only tell you the good bits.
Where VoIP wins:
Where it's worth pausing:
Not a system that's simply "better," but one that's better suited to how most businesses actually work now, provided the groundwork is checked first.
It's tempting to compare providers on feature lists. Most of those features, you'll never touch. The real question is which system fits how your team actually works, and who picks up the phone when something goes wrong.
A short, practical checklist:
Whether you're an Office Manager tired of chasing a supplier's call centre, an Operations Manager who needs the team reachable wherever they're working, or a Finance Director who wants one predictable monthly figure instead of a mystery bill, the answer to "which system" usually comes down to that last point more than any feature.
There's no shortage of VoIP providers in the UK, and most of their websites read exactly the same. Cut through it by checking three things: how they handle support when something goes wrong, whether their contracts lock you in past the point you'd want out, and whether they'll actually manage your migration or just sell you a login and leave you to it. A provider who disappears after installation isn't a partner, whatever the sales page called them.
There are two ways to run a VoIP system, and the difference matters more than most providers bother to explain.
Hosted VoIP means the provider runs everything off-site, in the cloud. You pay a predictable monthly fee per user, there's nothing physical to maintain in your building, and it scales up or down as your team changes. For most SMEs, this is the natural landing place, particularly with the 2027 deadline pushing everyone toward a decision now rather than later.
On-premise systems (an IP-PBX) mean the hardware sits in your building. Bigger upfront cost, you own and maintain it yourself, and you get more direct control over configuration. It still makes sense in specific cases: very high call volumes, particular integration or compliance needs, or a multi-line site where central control matters more than flexibility.
For the vast majority of businesses reading this, hosted wins on cost, on flexibility, and on not needing an engineer on standby. If your situation genuinely calls for on-premise, that's a conversation worth having properly, not a box to tick because it sounds more serious.
Real numbers, not vague ranges.
Worked example: a 10-user office on a mid-tier plan is looking at roughly £180 a month for the service itself, before optional handsets. Compare that to legacy ISDN line rental, which already sits at £25 to £50 per channel and is only getting more expensive before it disappears entirely.
Where people actually overspend isn't the software tier, it's the minutes bundle. A lot of businesses get sold a package built around call volumes they never come close to using. Check your actual usage before you sign anything, not what a salesperson assumes you'll need.
Here's what tends to go wrong with a VoIP migration: someone in the business gets handed the project alongside their actual job, discovers halfway through that the office broadband isn't up to it, and ends up managing three different suppliers who each blame the other when something breaks.
That's not how we do it. We become your IT department for this, not a phone provider who disappears after the install. That means:
One relationship. Not a platform, a login, and a phone number to call when it stops working.
The switch-off is real, the deadline isn't moving, and for most businesses this is genuinely a good move once it's handled properly. It doesn't need to be complicated, and it doesn't need to eat your week.
Not sure exactly what you're running or what you'll need before 2027? Book your 360 Review. No obligations, just a straightforward conversation with someone who knows IT and will tell you plainly what needs doing, and when.