If your business still relies on traditional phone lines, the clock is ticking. BT Openreach is permanently switching off the Public Switched Telephone Network (PSTN) and ISDN by the end of January 2027 — and that deadline is closer than it might feel.

This is not a minor technical update. It is the end of the analogue phone infrastructure that has underpinned UK business communications for decades. Here is everything you need to know, and what you should be doing right now.

What Is the PSTN Switch-Off?

The PSTN (Public Switched Telephone Network) is the traditional copper-wire telephone network that has been in use since the 1800s. ISDN (Integrated Services Digital Network) is the digital upgrade that most businesses moved to in the 1990s and 2000s. Both are now being retired.

BT Openreach announced the switch-off back in 2017. After several delays — including a pause during the pandemic — the final deadline is set for 31 January 2027. After that date, traditional landlines and ISDN connections will simply stop working.

This affects millions of phone lines across the UK, including business lines, ISDN2, ISDN30, and analogue services that businesses have relied on for years.

Who Is Affected?

The short answer: almost every business in the UK that uses a traditional phone line or ISDN connection. That includes:

• Businesses with traditional desk phones plugged into a wall socket
• Companies using ISDN2 or ISDN30 lines for their phone system
• Organisations using PSTN lines for broadband (ADSL/FTTC)
• Businesses using alarm systems, CCTV monitoring, door entry systems, or PDQ card machines that connect via a phone line
• GP surgeries, dental practices, and other healthcare providers on legacy systems
• Any organisation that has not yet migrated to a cloud or VoIP-based phone system

If you are unsure whether you are affected, check your phone bill. If it references ISDN, analogue lines, or a traditional BT line rental, you need to act.

The Timeline: Where Are We Now?

Openreach has been running a stop-sell programme since September 2023, meaning providers can no longer sell new PSTN or ISDN products. If your existing lines are up for renewal, you may already be finding that your current provider cannot extend your contract on the old technology.

The hard stop is 31 January 2027. That sounds like a while away, but migrating a phone system takes time — particularly for larger organisations. Procurement, installation, staff training, and number porting all need to be planned. Businesses that leave it until 2026 will be competing for engineer time and supplier availability with thousands of other organisations in the same position.

The sensible window to act is now.

What Do Businesses Need to Do?

The core requirement is straightforward: you need to move your voice communications to a technology that works over your broadband or fibre connection rather than a copper phone line. The main options are:

VoIP (Voice over Internet Protocol)

VoIP transmits calls over your internet connection rather than a dedicated phone line. It is reliable, cost-effective, and feature-rich. A well-configured VoIP system offers everything a traditional ISDN setup does — and considerably more, including call recording, voicemail to email, hunt groups, auto-attendants, and detailed call reporting.

Hosted / Cloud Phone Systems

A hosted phone system moves your PBX (the brains of your phone network) off-site to the cloud. There is no on-site hardware to maintain, updates happen automatically, and your system scales up or down as your business changes. Platforms like 3CX are particularly well-suited to UK SMEs — they offer a full-featured hosted or self-hosted option with desktop, mobile, and web clients included.

Microsoft Teams Phone

If your business already uses Microsoft 365, it is worth exploring Teams Phone. With the right calling plan or direct routing setup, Teams can become your full business phone system — meaning your staff can make and receive calls from the same platform they use for meetings, chat, and file sharing.

Do Not Forget Your Non-Voice Lines

Many businesses overlook the fact that PSTN switch-off affects more than just handsets. Alarm systems, ANPR cameras, EPOS terminals, fax machines, and door entry systems that connect via a phone line will all need to be assessed and potentially replaced or reconfigured. It is worth doing a full audit of every device on your premises that uses a phone line — not just the phones.

Why VoIP and Cloud Systems Are the Right Answer

The switch-off is an opportunity as much as it is a challenge. Businesses that move to a modern cloud phone system typically benefit from:

• Lower costs — no line rental, reduced call charges, and minimal hardware investment
• Greater flexibility — staff can work from anywhere with the same phone number and features
• Better features — call recording, CRM integration, call analytics, video calling, and more
• Easier management — add, remove, and configure users from a web portal without waiting for an engineer
• Business continuity — calls can be automatically re-routed if your office is unavailable

The businesses that migrate early — and do it properly — consistently report that they would not go back to their old system.

What to Look for in a Provider

Not all VoIP providers are equal. When choosing a partner to help you migrate, look for:

• Experience with UK business migrations, not just residential broadband
• Ability to port your existing numbers so you keep your business phone number
• A system that suits your size — from a single-site SME to a multi-site organisation
• Ongoing support, not just an installation and goodbye
• Familiarity with platforms like 3CX and Microsoft Teams Phone if these are relevant to your setup

Act Now — Do Not Leave It to the Last Minute

The PSTN switch-off is one of those technology transitions that many businesses know is coming but keep putting off. The difference with this one is that there is a hard deadline — and after January 2027, your phones will simply stop working if you have not moved across.

Planning a migration now gives you time to choose the right solution, negotiate the best deal, and ensure your team is comfortable with the new system before the deadline hits.

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Just Business Phones are VoIP and cloud phone system specialists based in Bolton. We work with businesses across the UK to plan and deliver smooth PSTN migrations — whether that means a hosted 3CX system, Microsoft Teams Phone integration, or a fully managed cloud PBX.

Contact Just Business Phones for a free consultation — we will assess your current setup and recommend the right solution.