How to move your business phone numbers to a new provider

What porting is and is not

A number port transfers the right to use a number from your current provider (the losing provider) to your new one (the gaining provider). The gaining provider requests it through an industry process, and on the agreed date the network starts routing calls to the new service. You do not need to cancel your old service first; in fact, doing so can lose the number entirely.

Porting covers landline numbers, 0800 and 0508 numbers and mobile numbers, though each type has its own process and timeframes. It does not move voicemails, call history or menus; those are rebuilt on the new system. Plan that build as a separate task, and save any voicemails or call recordings you need to keep before the old account closes, because they will not follow the number.

Gather the details first

Delays usually come from mismatched details. Get a recent bill from your current provider showing the account number, the exact account name and the billing address. List every number you want to move, including direct lines, fax numbers and any number ranges. Check which numbers are actually in use; porting numbers nobody needs only adds cost.

Find out who is the authorised account holder. The gaining provider will need a signed authority from someone the losing provider recognises. If the account is in a former director's name or a previous business name, sort that out with the current provider before you start, because it is the most common reason ports are rejected.

Build the new system before the port

Set up the new phone system completely before the port date. Create extensions, record greetings, configure the call flow and test using a temporary number the new provider issues. Make sure desk phones, apps and headsets work and that staff know how to answer and transfer. On port day, the only thing that should change is where calls arrive. Check that outbound caller ID is set to show your business number once the port completes. Also confirm any diverts, after-hours rules and voicemail-to-email are working. A port onto a half-built system means callers hear silence or the wrong greeting, which is worse than a short delay.

Timing the cut-over

Simple landline ports often complete within a week or two of a correct request, while complex ports with number ranges or multiple accounts can take longer. 0800 ports have their own process and timeframes. Ask the gaining provider for an estimated date and a cut-over window, and pick a quieter time of day or week if you can choose.

On the day, have someone available to test the moment the provider confirms completion. Ring each ported number from a mobile, check it lands where it should, and make an outbound call to confirm caller ID. Keep the old phone system connected until tests pass, in case calls briefly still arrive there.

Mistakes that cause outages

Cancelling the old service before the port completes is the classic error, and it can release the number back to the provider. Another is porting the main number but forgetting a direct line printed on business cards or an alarm line used by monitoring. Mismatched account names cause rejections that push the date out by days.

Do not forget the less visible places your number appears: your Google Business Profile, website, email signatures and invoice templates. If any of those carry a different number, decide whether to port it or update the listing. After the port, check your old provider's final bill to make sure services are closed and you are not still being charged.

After the move

Once everything has moved, close the old account in writing and keep the confirmation. Update your internal documentation with the new provider's details, the admin login owner and the list of numbers. If you also use the numbers for two-factor authentication on any accounts, check those still receive codes. Ask the new provider who should be called if a number stops working, and record it where staff can find it. Ports are usually smooth, but a clear record makes the next change easier too.

Keep an eye on inbound calls for the first week. If a customer mentions they rang and got an unfamiliar message, or call volumes look lower than usual, test each number again from a few different networks, including a mobile on another provider and an international line if you have overseas customers. Routing changes can take a short time to settle across every network, and a quick check catches a stray number before it costs you an enquiry. Once a full week passes cleanly, the port can be considered finished.