Yes, keeping your existing business number should be part of the move to VoIP. Ofcom's business guidance says number porting must be available on reasonable terms and conditions.[9] Before ordering, give the new provider every number you want to retain and ask it to confirm that it can transfer them onto the proposed service.
Do not cancel the old line as your first step. Ask the new provider to coordinate the transfer and explain what will happen to the services on your existing account. Your practical goal is simple: the number customers already use should reach the right people after the move, with a tested fallback if something goes wrong.
Confirm exactly which numbers are moving
Start with the main advertised number, then check invoices and the current phone system for direct dial numbers, department lines and any numbers used at other sites. Record who answers each one and what should happen when nobody is available. Do not assume the number printed on the latest bill is the complete set.
Send that inventory to the proposed provider before agreeing a transfer date. Ask which numbers it has accepted, which need further checks and whether moving part of a number range affects the rest. Keep written confirmation beside the order so an omitted line can be spotted before customers start reporting failed calls.
Check what else depends on the old line
Ask your current provider to identify the services attached to the account and confirm which will end when the number moves. Specifically ask about broadband, rented equipment and any bundled services. If replacement connectivity is needed, make its installation and testing a dependency of the phone move rather than a job for afterwards.
Openreach warns that analogue-connected equipment can be affected by the digital switchover, including alarms, payment terminals and lift phones.[1] Ask each equipment supplier to confirm compatibility and any replacement work. Keeping the telephone number does not establish that a connected alarm has been tested. Treat those checks as separate sign-offs, with a named person responsible for each.
Agree the transfer arrangements in writing
Ask the new provider what account details and authorisation it needs. Check the business name, account reference and service address against the existing provider's records rather than guessing from memory. Nominate someone who can answer questions during the transfer, and give that person a contact route that does not rely on the number being moved.
Get the agreed date, expected interruption and escalation contact in writing. Ask what happens if the transfer is rejected or only partly completes. Ofcom's guidance says that, if the number-porting process fails, the number and relevant services must be reactivated until it completes successfully.[9] Have the provider explain how it would handle that situation for your order.
Prepare the new phone system before the number arrives
Ask to test the new system using a temporary number before the main number moves. Try the handsets or apps staff will actually use. Walk through the opening-hours greeting, call transfers and voicemail, then check what a caller hears outside normal hours. Get the people answering the phones involved rather than leaving every test to the installer.
Plan for a local outage too. Openreach confirms that digital phone lines need power to work.[1] Ask the supplier to explain the proposed battery backup or alternative calling arrangements, and test the agreed fallback safely. Confirm emergency-calling arrangements with the provider, including the address it holds; do not make test calls to emergency services.
Test the number after the transfer
Once the provider reports completion, call each transferred number from an external mobile and another network where possible. Check that the right phone rings, speech works in both directions and transfers reach the intended person. Make an outgoing call and check the number shown to the recipient. Record results against the original inventory.
Repeat the checks for voicemail and out-of-hours routing. If anything fails, record the time, calling number and destination securely for the provider to investigate. Keep the issue open until a repeat test passes. Finally, ask the old provider to confirm which services remain active and check the closing invoice against the agreed changes.
Start with your number list
Openreach gives 31 January 2027 as the date for traditional phone lines to go digital.[1] Ask your provider about the timetable for your own service rather than treating that national date as an installation appointment. Leave room for equipment checks and staff training before the move.
For help planning the change, talk to BMT about business phone systems. Bring your number list, current phone and broadband bills, and details of any equipment using the line. That gives us a useful starting point for discussing the transfer and how you will check that it has worked.
Sources
[1] https://www.openreach.com/big-switch-off
[9] https://www.ofcom.org.uk/phones-and-broadband/coverage-and-speeds/gen-conditions