Black BT Versatility ISDN business desk phone with coiled handset cord and unplugged RJ11 connector, lit by a single hard overhead key on a Gray 10 surface
BT switch-off deadline · January 2027

The PSTN switch-off, explained.

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JAN 2027

The PSTN switch-off deadline. After this date, your existing copper line stops working — no exceptions, no extensions.

The deadline is real, and most UK SMEs aren't ready.

BT is shutting down the PSTN and ISDN networks that have carried UK business phone calls for forty years. Every BT landline, ISDN30, ISDN2e, and most "Featureline" and "Featurenet" services stop working by January 2027. Some local exchanges are switching off earlier.

The replacement is internet-based: SIP trunks running over your existing broadband, connecting to a hosted phone system. The system Port Phones runs is 3CX — the same platform used by hundreds of thousands of businesses worldwide.

Most of our customers save 40–60% on monthly phone costs versus their old BT bills. The bigger win is they stop worrying about it.

Switch-off deadline
Jan 2027
Engineering availability is already limited in busier postcodes. Don't leave it until Q4 2026.

How the migration works.

Three steps, no disruption to your phones during the changeover.

01

Free audit

We review your current setup in a 15-minute call. We tell you which BT lines you're on, what needs to change, what it'll cost, and the timeline.

02

Parallel build

We build the new 3CX system and test it alongside your existing BT lines. The new and old phones run in parallel until cut-over. You keep your existing numbers.

03

Cut-over and stay live

On a quiet day, we port your numbers from BT to the new SIP trunks. The old phones go silent, the new ones light up. We're on call for the first week.

Frequently asked questions.

Everything you need to know about the switch.

BT is shutting down the old copper phone network (PSTN) that has powered UK landlines for decades. All traditional phone lines, ISDN lines, and services that depend on them (alarm dialers, lift lines, payment terminals tethered to a phone line) will stop working by January 2027. Every UK business using a BT landline needs to move to an internet-based phone system (VoIP) before then.
Yes. We port (transfer) your existing numbers from BT to your new system. Your clients, suppliers, and letterheads all stay the same. The porting process typically takes 10–30 business days and we handle the entire process end to end.
Probably not all of them. If you already have IP phones (the kind that plug into your network with an Ethernet cable), they'll almost certainly work with 3CX. If you're still using old analogue phones connected to a wall socket, those need replacing. We tell you exactly what's needed during the free audit and supply Yealink IP phones at trade prices, not marked up.
From signing up to going live, typically 2–4 weeks. We build the new system and test it alongside your existing phones first, so there's no disruption. The actual switch-over happens on a quiet day and takes a few hours. We're on call for the first week after.
Usually not. A modern business broadband connection handles VoIP calls without any issues. As a rough guide, each simultaneous call uses about 100Kbps, so even a basic 30Mbps connection comfortably supports hundreds of concurrent calls. We check your connection quality during the audit and tell you up-front if there are any concerns.
These are the easy-to-miss casualties of the switch-off. Anything that dials out over a copper line (alarm-to-monitoring-station dialers, lift emergency phones, EFTPOS terminals on a phone line, fax machines) needs a plan. We flag them at the audit and either replace them, move them to a dedicated SIP line, or refer you to the right specialist if it's outside our scope.

Book a free PSTN-readiness audit.

15 minutes. We review which BT lines you're on, what needs to change before 2027, and how much it'll cost.

What you get from the audit

A clear picture of your current phone setup, what needs to change, a timeline for migration if you proceed, and a fixed-price quote with the cost stack broken out line by line. No jargon, no pressure.

Prefer to call or email?

+44 7909 338388
sales@portphones.co.uk
31-33 Commercial Road, Poole, Dorset BH14 0HU

Why audit now, not in Q4 2026?

Engineer availability for on-site work is already tight in busier postcodes. The closer to the deadline, the longer the lead time. Audit costs nothing and locks your slot in the calendar.

Book the audit