How to Keep Your Business Number After the PSTN Switch-Off

Your business number is more than a contact detail. It’s on your van, your website, your Google listing, your invoices and your customers’ phones. Changing it costs time, money and customers. The good news: you don’t have to change it. Even after the PSTN switch-off on 31 January 2027, your number can come with you.

Here’s exactly how.

What is the PSTN switch-off and why does it affect your number?

The PSTN (Public Switched Telephone Network) is the traditional copper phone network that has carried UK calls for decades. On 31 January 2027, BT switches it off. No extensions. No exceptions.

If your phone line currently runs over PSTN or ISDN, it will stop working on that date. But your number doesn’t have to go with it. Phone numbers in the UK are portable: you can move your existing number to a new provider and a new technology without losing it.

The process is called number porting, and it’s straightforward when you do it properly.

What is number porting?

Number porting is the process of transferring your existing phone number from one network or provider to another. It happens in the background. Your customers won’t notice anything. Your number stays identical, the same 01, 02, 03 or 08 number you’ve always had.

TTNC is a true network operator with a 7 million-plus number inventory and extensive porting experience. We port numbers, including virtual numbers, onto our own hosted voice platform, which means your number is on infrastructure built to last well beyond 2027.

Can I keep any type of number?

In most cases, yes. The numbers most commonly ported are:

Geographic numbers (01 and 02) are the most common porting request and entirely straightforward. Your local area code and number stay with you.

Non-geographic numbers (03, 0800, 0344, 0333) can also be ported in the majority of cases. If you’ve built a brand around an 0800 or 0333 number, you can keep it.

DDI ranges on ISDN can typically be migrated to a hosted SIP platform and retained in full.

If you’re unsure about your specific number type, our team will check it as part of a free migration consultation.

How does the porting process work?

The process is simpler than most businesses expect.

Step 1: We check your number. You tell us what you want to keep. We verify it’s portable and confirm the requirements.

Step 2: You authorise the port. You sign a Letter of Authority (LOA), which tells your current provider you’re moving to TTNC. It takes a few minutes.

Step 3: We handle the rest. TTNC submits the porting request and manages the transfer with your current carrier. You don’t need to chase anyone.

Step 4: Your number goes live on the new platform. On the agreed porting date, your number transfers. For most ports, this happens with zero downtime.

Step 5: You manage it from your myTTNC portal. Route it, add features and stay in control from day one.

Typical geographic number ports complete within five to ten working days. Our team will give you a confirmed timeline upfront.

When should you start?

Now. The closer to 31 January 2027 you leave it, the more pressure on every porting queue in the industry. Carriers and support teams will be under strain in the final weeks, and delays in that period are harder to manage.

Businesses that start migration now avoid the January rush entirely. Porting your number while your PSTN line is still active is also cleaner. There’s no gap in service and no emergency re-routing required.

If you have a DDI range or are migrating multiple numbers, allow extra time. We’ll scope this with you during the consultation.

What if my PSTN line has already been switched off?

Numbers can typically only be ported while still active on a network. If a number has been disconnected, recovery isn’t always possible. This is the single biggest risk of leaving migration too late. Don’t let it happen to your number.

What does porting cost?

TTNC doesn’t charge for standard number porting as part of a new hosted voice or Switch-Off Ready package. You keep your number and get a hosted platform built for the next decade.

Ready to protect your number?

The switch-off is fixed. Your number doesn’t have to be at risk. Whether you’re on a single geographic number or a DDI range, TTNC will handle the porting and the migration.