Can I keep my PSTN number when I switch to VoIP?

When you're ready to switch landline to VoIP, keeping your existing business number is usually the very first question on every business owner's mind. Transferring your old PSTN landline to your new VoIP system doesn't have to mean losing the contact details you've built your business around. After all, your telephone number is most likely very important for your business. Many of your existing customers have that number stored in their files, and you've accumulated many contacts, perhaps over multiple years.

Changing your contact adds a lot of work and pressure, as you will need to inform everyone of the change, and those people might not even get the memo. Simply moving the existing landline phone number across, rather than starting again with a brand new one, is most likely the easiest option for your business.

Whether you're looking at how to switch from landline to VoIP for a single office line or you're planning to port an entire estate of business numbers, the good news is that transferring a landline number to VoIP in the UK is a well-established process. Providers do this every single day, and in the vast majority of cases your number, your reputation and your customer relationships stay completely intact.

A PSTN (Public Switched Telephone Network) is commonly known as a traditional telephone line. Simply put, a PSTN line lets users make landline telephone calls to one another over copper cabling. This method allows one conversation to be conducted on one analogue telephone line using that single phone contact, meaning that you cannot have multiple calls on one number at the same time.

So, what is a PSTN number in practical terms? It's simply the landline number assigned to that analogue circuit, the one printed on your shopfront, your invoices and your Google listing. A PSTN landline has served UK businesses well for decades, but it's a fundamentally different technology to a VoIP pstn phone setup, which sends your calls as data over the internet rather than down a physical copper line.

Having a PSTN line may suit your company now if you're a sole trader or small business owner with a limited need for landlines. However, with BT's impending 2027 'The Big Switch Off' coming right around the corner in a few short years, now is the time to consider transferring PSTN to alternatives, such as VoIP.

Find out more about BT's "The Big Switch Off", how it will affect your business and what you can do to transition in our blog: ISDN Switch Off - Everything you need to know.

Can you keep your old PSTN contact when switching? Yes, all numbers can be transported, but there can be a few exceptions. The only real exceptions are numbers with special features, such as ISDN. But in most cases, there will be an easy transfer from landline to VoIP.

With this in mind, as you are required to switch before 2027, will your business want to keep its old contact when switching? If your number is valuable to you, then keep reading to find our tips and advice on how to keep your number when switching.

Can I keep my landline phone number if I switch providers in the UK?

Yes. Whether you're asking "can I keep my landline number if I switch providers" for a single office line, or you're a larger organisation wondering "can I keep my landline phone number with full fibre", the answer in almost every case is the same: your number belongs to you, not your provider, and UK regulation (Ofcom's number portability rules) protects your right to take it with you. This applies whether you're switching landline provider and want to keep your number, moving from one VoIP supplier to another, or even asking whether you can keep your landline number with voip when you upgrade your broadband to full fibre.

Can I keep my number if I move house or office?

It's a slightly different question, but a common one: can you keep your landline phone number when you move premises? Generally, keeping your exact same geographic landline number when relocating to a different exchange area isn't always guaranteed with a traditional PSTN service, since landline numbers are historically tied to a local exchange. This is actually one of the hidden benefits of moving landline number to VoIP: because your number is hosted in the cloud rather than tied to a physical line, keeping your landline number when moving office (even to a different town) becomes far more straightforward. So if you're planning a move and want to keep home phone number continuity, switching to VoIP first is often the smart route.

Before we go further into porting, it's worth quickly covering what VoIP actually is, since it underpins everything else in this guide. VoIP stands for Voice over Internet Protocol, a way of making and receiving calls as data over your broadband or leased line connection, rather than through a dedicated copper PSTN circuit. Instead of a physical phone line, your calls travel as digital packets, much like sending an email or streaming a video.

This is why the shift from PSTN to VoIP is sometimes described using terms like a "pstn to voip converter" or "pstn to sip converter" — in essence, these describe the technology (an ATA, or analogue telephone adapter, or a SIP trunk) that bridges your existing analogue handsets or PBX to a modern, internet-based network. If you've got older equipment you're fond of, a voip adapter can often let you keep using it, simply converting the signal so it runs happily over your internet connection instead of the old exchange line.

In terms of hardware, you've got a few options when you move to VoIP: a dedicated VoIP phone (also known as an IP phone) that plugs straight into your network, a softphone app on your computer or mobile, or an adapter that lets your existing handsets carry on working as normal. Whichever route you choose, the underlying principle is the same: your number is no longer tied to a single physical line, it's hosted in the cloud and can ring on almost any internet-connected device, anywhere.

Keeping your business contact makes it much simpler for you and your pre-existing customers to stay connected. It then makes sense to keep your old number when transferring phone systems. The good news is that keeping your phone number when making the transition is easy, because your next provider will take care of the porting for you.

The most work that you will need to conduct when transferring your numbers is getting hold of a few pieces of information for your new provider. This is true whether you're porting a single landline number to VoIP or handling a bulk transfer of an entire business phone line estate.

As we have mentioned, transferring your old Public Switched Telephone Network number is much simpler than you think. We've broken down the steps to make that easy transition from your old number to your new VoIP system.

1. Before selecting a supplier, make sure that your intended VoIP provider offers a ported number service, especially if keeping your number is valuable to your business. Not every provider handles every type of port, so it's worth confirming they can manage porting a landline number to VoIP before you sign up.
2. When you've found your new provider and before transferring your number, do not cancel your old telephone service, as you will need it in place to port your old number across.
3. Once your account is set up with your new supplier, they will most likely need details from you. They may ask you to go online and fill in some information about the number you want to transfer and the required timing. You may also need to note your account holder's name and address. Unlike mobile number porting, you generally won't need a PAC code (that's only given to a new mobile provider) — landline and VoIP porting instead uses a Letter of Authority or online form, so don't worry if nobody asks you for one.
4. When you have updated your details with your new provider, enquire about a time frame from them as to when your service goes live; this will give you an indication of when to cancel your old phone service.
5. Once your number is transferred and everything is set up, you can cancel your previous telephone service.

There we have it: transferring your old number and using your new VoIP system can be as easy as that. All your next supplier will need is a few simple details, and they will do the rest for you. This is exactly the same principle whether you're asking how to port an existing number to VoIP for a business switchboard, or simply want to know how to port a landline number for a single-line sole trader setup.

The process of switching from your traditional landline provider to a VoIP service supplier is as simple as contact porting, as they will handle the transfer for you. They will deliver simple instructions on transferring your current landline number to your new provider. There are, however, a few things that you will need to check first before making the switch, which is as follows:

• Make sure you have the correct VoIP equipment in your business already. If you do not have the right equipment, you may need to invest in some new tech, such as IP handsets, a suitable router, or a voip adapter for any older analogue devices you want to keep.
• Check your internet connection and its speed. VoIP runs over the internet, so you will need a reliable and efficient connection so that your phone line works most effectively and without issues. If it is patchy, you may need to research different internet providers or consider leased lines (find out more about leased lines in this blog).
• Research VoIP providers UK-wide to ensure that you are choosing the best system for your business that aligns with your communication needs, company size and budget. Not all VoIP services that let you keep your landline phone number are created equal, so compare support, reliability and porting experience, not just price.

If you're wondering how to switch phone providers and keep your number more generally, whether that's moving from one VoIP provider to another down the line, or switching business phone line suppliers entirely, the process above stays broadly the same. Switching VoIP providers is often even quicker than the original PSTN to VoIP switch, since the number is already hosted digitally and simply needs re-pointing to your new supplier's network.

A huge number of the businesses we speak to are specifically looking at how to replace a BT landline with VoIP, since BT and Openreach still supply a large share of the UK's traditional PSTN lines. If you're currently with BT and wondering how do I replace my BT landline with VoIP, the process is exactly the same as any other porting job: choose your new VoIP provider, confirm they support BT number transfers, and let them handle the paperwork to transfer your BT landline number to VoIP.

You may also see the term "Gamma PSTN switch off" mentioned online. Gamma is one of the UK's largest wholesale network providers (and the platform behind products like Gamma Horizon, mentioned below), and it is aligning its own network changes with the wider industry-wide 2027 PSTN and ISDN switch off. In practice, this simply reinforces the same message: whichever provider currently supplies your PSTN line, whether that's BT, Gamma, TalkTalk, Sky or another landline provider, now is the time to plan your move rather than wait until the switch off date creeps up on you.

Porting a BT number to VoIP, or indeed porting any provider's number to VoIP, doesn't require you to have any special negotiating skills. Your new VoIP provider effectively does the "translating" between networks on your behalf, requesting the transfer from your outgoing provider and keeping you updated on timescales.

One of the most common questions we hear is whether you can move landline to VoIP for free. The porting process itself, the actual transfer of your number from your old PSTN network to your new VoIP platform, doesn't typically carry a separate porting fee from most reputable UK VoIP providers; it's usually built into your onboarding as standard. So in that sense, a free transfer of your landline number to VoIP in the UK is very much the norm, not the exception.

Where costs can appear is if you're still tied into a minimum term contract with your existing PSTN or landline provider. Ending that agreement early may trigger an early termination charge, which is separate from the porting itself and is worth checking before you commit to a switch date. It's also sensible to confirm with your new VoIP provider exactly what's included, some may offer inclusive setup and hardware as part of a package, while others charge for handsets or installation separately.

If you are a small business, such as a shopkeeper, freelancer or restaurant, you are most likely using an analogue phone line. However, if you are a larger business with an on-site PBX, you might prefer to keep your existing equipment and update it to adapt to the change.

How many users you intend to use on the cloud-based phone system depends on the type of phone system that would be best for your business. Different communication systems are designed for various user numbers, and choosing the right one makes moving your business number to VoIP feel far less daunting.

Phoneline+: Recommended for small businesses

If you are a smaller-sized business with 1 - 3 users, opting for a simpler system might work best for your business, such as Phoneline+.

Phoneline+, also known as the "simple phone line replacement service", is a great cloud phone service designed for small businesses. It is everything you can do on your traditional line and allows you to keep your existing company numbers and make or receive voice calls from internet-ready devices. If Phoneline+ is the phone system that you've been looking for, get in touch with us today for more information and advice.

Gamma Horizon: Recommended for businesses looking to grow

If you are a medium-sized business with a few more users, or a small company looking to grow, you may want to consider a cloud phone system with more features, such as Gamma Horizon.

Gamma Horizon is an excellent cloud-based phone system that is great for businesses of all sizes and those looking for a fully managed service. If Gamma Horizon is the phone system that you've been looking for, get in touch with us today for more information and advice.

Joining T2K is one of the best if not the best business decisions we've made.

Paul Crisell - Vale Veterinary Clinic

5.0

on Google

Compare Phone Systems

We get asked a huge range of questions around switching landline to VoIP and porting numbers, so we've pulled together some quick answers to the ones that come up most often.

Can I transfer my landline number to a mobile?

Yes, in many cases you can port a landline number to a mobile-compatible VoIP number, meaning calls to your old landline can ring through to a mobile app or handset instead. This is popular with sole traders and smaller teams who want the flexibility of a business number without being tied to a desk. The reverse is also possible in some setups, with a mobile number to landline style routing, depending on your provider's platform.

How long does it take to port a number to VoIP?

Most landline-to-VoIP ports complete within a couple of weeks, though it can vary depending on your outgoing provider and the complexity of your existing setup. Your new provider will always confirm an expected go-live date once your details have been submitted, so you know exactly when to stop relying on your old service.

Can I switch VoIP providers again later and keep my number?

Absolutely. Once your number has been ported into the VoIP world, switching VoIP providers again in future is usually even simpler than the original PSTN to VoIP transfer, since it's already hosted digitally rather than tied to a physical exchange line.

What about Google Voice or other consumer platforms?

Google Voice and similar consumer-grade services are generally aimed at individual users rather than UK businesses, and porting a UK landline number into them isn't always straightforward or guaranteed. For business use, a dedicated UK VoIP provider that specialises in business number porting will almost always give you a smoother, more reliable outcome, along with proper business features like call queuing, hunt groups and inclusive support.

Do I need to tell customers I've switched providers?

Because your number stays exactly the same throughout the switch, most of your customers won't notice any difference at all beyond, hopefully, clearer call quality and fewer dropped lines. There's no need for a mass "we've changed our number" announcement, which is precisely why so many businesses choose to keep their existing landline number rather than start fresh.

Is it time that you made the switch from PSTN to VoIP? Then T2k is here to help. We're communication experts, helping small businesses to large corporations with their telephone systems for over 25 years. Our expert advisers are here to help you select the right phone system for your company and make the transition as easy as possible. We are also there to help with number transition so that you do not lose those hard-earned contacts. For a jargon-free conversation on how to transition from PSTN to VoIP, contact T2k today.