The UK’s traditional telephone network — known as the Public Switched Telephone Network, or PSTN — has reached the end of its life. Openreach’s long-announced plan to retire the copper wire telephone infrastructure that has underpinned UK landlines for decades is now well underway, and businesses still running on legacy PSTN or ISDN systems need to act.

If you’re not sure what any of that means for your business, read on.

 

 

 

What Is PSTN and Why Has It Been Switched Off?

 

PSTN — the Public Switched Telephone Network — is what most people simply call a landline. It’s the traditional copper wire telephone infrastructure designed for analogue voice communication. ISDN (Integrated Services Digital Network) is a digital evolution of the same copper-based system, commonly used by businesses for multiple phone lines.

Openreach announced the retirement of both PSTN and ISDN services as part of the UK’s broader shift to a fully digital telecommunications network. The goal is straightforward: move every UK phone line onto internet-based infrastructure, replacing analogue copper with fibre and digital services.

As of 2026, Openreach has stopped accepting new PSTN and ISDN orders across the UK, and the full switch-off is actively rolling out region by region. Businesses in some areas may already have lost their legacy service, while others are still within the transition window — but that window is closing.

 

 

 

What Replaces PSTN and ISDN?

 

The replacement for PSTN and ISDN is VoIP — Voice over Internet Protocol. Rather than routing calls through copper telephone lines, VoIP transmits voice calls as data over your internet connection. It’s a technology that has been in widespread business use for over two decades, and for most organisations it delivers a significantly better experience than the legacy system it replaces.

If your business is already running a VoIP phone system, you’re ahead of the curve and no immediate action is required on the switch-off itself — though it’s worth reviewing whether your current VoIP setup is performing as well as it could be.

 

 

 

What Are the Benefits of Switching to VoIP?

 

The PSTN switch-off isn’t just an infrastructure change to manage — it’s an opportunity to upgrade your business communications in ways that legacy phone systems simply couldn’t support.

 

Lower Call Costs

VoIP calls, particularly internal calls between staff and calls to other VoIP numbers, are significantly cheaper than traditional landline calls. For businesses with multiple sites or remote workers, the savings can be substantial.

 

Flexibility and Remote Working

VoIP phone systems aren’t tied to a physical location. Staff can make and receive calls on their business number from anywhere — whether that’s the office, home, or on the road — using a desk phone, laptop, or mobile app. For businesses operating hybrid working models, this is a genuine operational advantage.

 

Advanced Features as Standard

Modern VoIP systems come with features that would have cost a premium on legacy systems — call routing, auto-attendant, voicemail to email, call recording, and hunt groups are typically included as standard. These tools help businesses present a professional image and manage calls more efficiently.

 

Scalability

Adding or removing phone lines on a VoIP system is straightforward and doesn’t require an engineer visit. As your business grows or changes, your phone system can adapt quickly and cost-effectively.

 

Integration with Microsoft 365

For businesses using Microsoft 365, VoIP systems can integrate directly with Microsoft Teams — enabling calls, video conferencing, and messaging from a single platform. This is increasingly how modern businesses manage their communications.

What Should You Do If You’re Still on PSTN or ISDN?

If your business is still running on a legacy PSTN or ISDN system, the priority is to migrate to VoIP as soon as possible. Waiting until your legacy service is forcibly terminated risks unexpected downtime and a rushed migration — neither of which is good for business continuity.

The migration process itself is straightforward when managed properly. Your existing business phone numbers can typically be ported across to your new VoIP system, meaning customers and suppliers experience no disruption.

At Via Wire, we design, supply, and manage VoIP phone systems for businesses of all sizes. Whether you’re migrating from a legacy PSTN system or looking to upgrade an existing VoIP setup, our team handles the process from start to finish — including number porting, hardware, and ongoing support.

Get in touch today to discuss your business phone system requirements.