What Happens to My Number When You Switch VoIP Provider?

In almost every case, your business number moves with you when you switch VoIP provider and keeps working exactly as before — same number, same look and feel to callers, no need to update signage, marketing or business cards. This happens through a process called porting, which transfers the number itself from your old provider to your new one, rather than giving you a temporary replacement while things are set up.

Does a Phone Number "Belong" to a Provider or to You?

Neither, technically — and this is worth understanding because it's why porting works the way it does. UK phone numbers are allocated by Ofcom to providers, but once a number's assigned to your account, you have the right to take it with you if you switch providers. No provider can refuse to release a number you're actively using, as long as your account is in good standing.

What Actually Happens During the Switch?

Your new provider requests the number from your current one, using your account details and a signed Letter of Authorisation. Once validated, a switchover date is agreed, and on that date, the number is redirected to your new system. Calls to that number start arriving through your new provider from that point onward.

Throughout this, the number itself never changes — only which system it's connected to does.

Will There Be Any Downtime?

There shouldn't be, provided the switch is managed properly and your old service stays active right up until the new one is confirmed working. Most downtime issues during a provider switch come from cancelling the old service too early, not from the porting process itself failing. A well-managed switch is designed so callers notice nothing at all.

What Happens to Your Old Provider Account?

Once the number's fully ported, your old provider loses the ability to route calls to it — that number is now entirely with your new provider. Your account with the old provider typically needs to be formally closed separately, since porting the number doesn't automatically cancel any remaining contract or billing with them. It's worth checking your notice period and any early termination terms before switching, so there are no surprises on the old side.

Are There Numbers You Can't Keep?

The vast majority of UK geographic and non-geographic business numbers can be ported without issue. A few situations are worth flagging:

• Mobile numbers generally port between mobile networks, not into a fixed VoIP business system, since they're a different type of number range
• Numbers with an unusual porting history — moved multiple times already — sometimes need extra verification, which can add time but doesn't usually block the port outright
• Numbers tied to specific legacy exchange technology occasionally need extra checks, though this is increasingly rare as providers move away from older infrastructure

If you're ever unsure whether a specific number can be ported, it's worth checking with your new provider before assuming either way.

What Happens to Your Features?

Porting moves the number itself, not your call routing, auto attendant menus, voicemail greetings, or forwarding rules — those need to be rebuilt on your new system. This is actually useful, since it's a natural point to review whether your existing setup still reflects how the business actually works, rather than just recreating years-old settings by default.

Frequently Asked Questions

Can I switch providers without porting my number? Yes, technically, but you'd end up with a new number, which most businesses want to avoid given how much a number appears across marketing, signage, and existing customer relationships.

Do I need to tell customers when I switch VoIP provider? No, not if the number stays the same and the switch is managed without downtime — from a caller's perspective, nothing changes at all.

Can I switch back to my old provider later if I change my mind? Yes, numbers can generally be ported back, following the same type of process in reverse, though it's worth checking any minimum contract terms with your new provider first.

Does switching provider affect my number's local area code? No. Your area code and number stay exactly the same regardless of which provider or system you move to.

A number switch should be invisible to your customers if it's planned properly. Request a quote for independent advice on switching to Gamma Horizon or 3CX, or read our guide to how long porting takes if you're planning around a specific date.