The question that stops most Teams migrations before they start is whether you keep your phone numbers. You do. The main number that is printed on the vans, the direct dials people have saved, the number on your Google listing: all of it moves across. What catches businesses out is not whether it can be done, it is the order things have to happen in, and what quietly delays it.
The 30-second version
- Your numbers move with you. Porting into Teams works like porting between any two providers.
- Never cancel the old service first. This is the one mistake that genuinely loses numbers.
- Details have to match exactly, and mismatched account details are the biggest single cause of rejection.
- The main billing number matters, because porting it can close the whole account underneath it.
- Emergency service addresses need setting properly, and this is not optional.
On this page
What porting into Teams actually involves
Porting is the process of moving a number from one provider to another while keeping the number itself. It has nothing to do with Microsoft specifically, and it works the same whether you are moving to Teams, a hosted phone system or anything else.
What is different with Teams is what happens at the far end. The number arrives, gets assigned to a user, a resource account or a call queue, and from that point their Teams app rings. The work is mostly paperwork and sequencing rather than technology.
The order things have to happen in
- Agree what is moving. Main number, direct dials, ranges, the fax number nobody admits to still having. Get the full list off your current bill rather than from memory.
- Get your licensing and routing sorted first, so there is somewhere for the numbers to land. Our guide to Direct Routing, Operator Connect and Calling Plans covers that choice.
- Submit the port with details that match the losing provider exactly. Company name, address and account number as they appear on their system, not as you would write them.
- Agree a date and plan the cut-over, ideally not on your busiest morning of the week.
- Test after the port completes, calling in and out, and check the numbers land on the right people and queues.
- Only then cancel anything. The old service ends as part of the port, and cancelling ahead of it is how numbers get lost.
The mistake that actually loses numbers
Cancelling the old line before the port completes. Once a number is disconnected you have a short window to recover it and after that it is gone. Nothing about moving to Teams requires you to cancel anything early, so do not.
The five things that delay a port
| What goes wrong | Why it happens |
|---|---|
| Details do not match the losing provider | A trading name instead of the registered name, or a new address after a move. Ports are matched exactly and rejected on any difference |
| The main billing number is in the list | Moving it can close the account and everything under it. It usually has to go last, or be handled separately |
| Numbers are on a contract with time left | The port still happens, but early termination charges may apply, and it is better to know before than after |
| Nobody knows the full range | Direct dial ranges get part ported, and the numbers left behind stop working. The bill is the source of truth here |
| The losing provider is slow | Some are. It is not a reason to cancel and start again, which is exactly what it tempts people into doing |
None of these are dramatic on their own. They are just the reasons a port that should take a couple of weeks takes two months, and almost all of them are avoided by getting the detail right on the form at the start.
Emergency calls, and why the address matters
On a traditional phone line, an emergency call carried the address of the line with it. With Teams, the app can be anywhere, so the address associated with a user has to be set deliberately rather than assumed.
This is not administrative box ticking. If somebody dials 999 from Teams, the address configured is what the emergency operator sees. It needs to be right, it needs updating when people move desks or sites, and it needs checking as part of the migration rather than afterwards.
Worth doing at the same time
Take the opportunity to work out which equipment in the building is still on an analogue line. Lifts, door entry, alarms and card terminals do not move to Teams, and a phone migration is exactly when people discover them. Our PSTN switch-off guide covers what to look for.
What cut-over day actually looks like
Less dramatic than people expect, when it is planned. The numbers move at an agreed time, usually in a window rather than instantly, and calls start arriving in Teams instead of the old system.
The things worth having ready are a list of who should be testing what, somebody available on both sides, and a fallback for the first hour or two such as a mobile answering the main number. In practice the most common issue is not the port failing but a number landing on the wrong user or queue, which takes a minute to fix if somebody is watching for it and half a day if nobody is.
Moving numbers is the bit people worry about.
Send us your latest phone bill and we will tell you exactly what you have, what moves, what needs handling separately and how long it realistically takes. It is the quickest way to get a straight answer.