The PSTN & ISDN switch-off isn’t a 2027 problem. It’s a 2026 problem.

BT is raising prices on analogue and ISDN lines by 40% from 1 October. With roughly 52,000 legacy lines still active across UK businesses, every month of delay now costs more than the last.

And price is the smaller issue.

When the January 2027 shutdown lands, these lines simply stop working — no grace period, no fallback. For many businesses, that’s not just a phone system. It’s:

• Customer and supplier communication lines
• Business-critical phone systems
• Security and alarm systems
• Lift and emergency call lines
• Payment terminals and connected devices
• Internal operations running quietly in the background

The hardest part isn’t the migration itself — it’s finding out what’s actually connected to these lines before they’re switched off. Lines installed a decade ago often outlive the people who remember what they’re for.

A telecoms audit fixes that. Five steps:

1. Identify – every PSTN and ISDN service still in use
2. Map – which numbers, devices and systems rely on them
3. Assess – what’s actually business-critical
4. Plan – the right replacement and migration path
5. Test & switch – with enough runway for a controlled transition, not a scramble

January 2027 feels distant. It isn’t — not once you account for install time, testing, and the queue every telecom provider is about to face.

At Pen Telecom, we help businesses map their legacy estate, flag the risks, and migrate with minimal disruption.

Don’t wait for a dead line to tell you what depended on it.

📧 service@pen-telecom.co.uk