Switching mobile operator and keeping your number

Your number travels, and moving it is not your job. In Belgium, porting a residential mobile line is not billed and completes one working day after the agreed date. It does not, however, wipe out what you still owe on the old contract. That is where the bill lands.

Who starts the transfer of your number?

The new operator, and only the new operator.

You sign with them, you tick the "I keep my number" box, you give the number to port, and they handle the rest: the porting request sent to the old operator, then the termination of the old contract on the switchover date. You have no cancellation letter to send, no call to make to the operator you are leaving.

The procedure is governed by the Royal Decree of 2 July 2013 on number portability, supervised by the BIPT (Belgian Institute for Postal Services and Telecommunications). It is not a commercial gesture each operator arranges as it pleases: the deadlines, the absence of charges on residential lines and everyone's obligations are written into it.

The consequence is brutal, and it kept me busy for three years in the cancellations department of a Belgian virtual operator. A number you cancelled yourself is a released number. It goes back into quarantine with the operator that assigned it, and nobody can port it any more, not you, not the new operator, not the support agent who swears otherwise. I have seen people lose a number they had held for eighteen years because they wanted to do things in order, except the order was the opposite of the one they imagined.

How long does porting take in Belgium?

One working day after the switchover date you agreed.

The actual outage is counted in minutes: the old SIM loses the network, you insert the new one or activate the eSIM, and the number picks up the new network. A confirmation text arrives shortly after. What really stretches the calendar is not the port, it is postal delivery of a physical SIM, when you have not gone the eSIM route.

The five steps, in order

None can be skipped, and the second one protects everything else.

1. Compare before you sign. The mobile plan ranking orders them on 24-month cost, handset counted separately, and the comparison tool puts them side by side, criterion by criterion.
2. Ask your current operator in writing for the exit statement. Any early termination fee, the handset balance, any discount clawback. Do it before signing elsewhere, not after.
3. Subscribe with the new operator and request porting. The number to port, the desired switchover date, and the identifier of your current SIM if you are asked for it.
4. Wait for the SIM card or the eSIM QR code. Cancel nothing in the meantime.
5. Activate on the agreed date. Check outgoing calls, incoming calls and texts that same day, not the following week.

What is still owed to the old operator?

Everything that is not the number.

This is the item nobody prices for you at the counter, and it is the one that runs into hundreds of euros. Porting moves a line. It cancels no financial commitment entered into elsewhere, and Belgian law draws a very clear line between the two.

Take the most common case I see: a handset financed over twenty-four instalments of €25, so €600 of hardware. You leave in month ten. Fourteen instalments remain, so €350 falls due, in one go, on the closing invoice. The plan itself can be terminated without a fee, since the contract has passed six months of performance. Two regimes, one invoice, and a €350 gap between the two lines.

The same departure in month five stacks both: nineteen instalments remaining, so €475, plus an early termination fee on the service, whose amount sits in your specific terms and which most Belgian operators do not publish on their website. When the box is not published, I do not estimate it: I ask for it in writing, and I keep the answer.

Does Easy Switch apply to a mobile-only line?

No, and the confusion is common because the two procedures look alike from a distance.

Easy Switch is the Belgian mechanism that lets a new operator take over a set of services: internet, television, fixed and mobile bundles. It works with a unique identifier printed on your invoice. A mobile-only line falls outside that scope: the standard porting procedure takes over, with the same practical effect, termination of the old contract by the new operator.

That detail matters if you are leaving a bundle. Pulling the single mobile line out of a Proximus or Telenet bundle can drop the multi-service discount applied to the rest of the household, and that discount has nothing to do with your number.

Line cut off during the transfer: what to do

Report it to the new operator the same day. They drive the request, so they are the ones who have to unblock it, and a ticket opened on the right date is worth more than a catch-up call three weeks later.

Keep a written trace: date, time, file reference, name of the person you spoke to. If the number is still not active after the announced deadline and support is going in circles, the Telecommunications Ombudsman Service handles disputes between Belgian consumers and operators at no cost to the consumer, and the BIPT supervises compliance with porting deadlines. A dated complaint is the only thing that makes those remedies usable.

Which mistakes cost people their number?

Five, and I have seen every one of them several times.

• Cancelling the old plan yourself, before or during the subscription. The number is released, porting becomes impossible.
• Letting a prepaid card expire before requesting the port. A prepaid number inactive for too long is taken back by the operator.
• Porting a number that is not in the applicant's name. A line belonging to a former partner, a parent or an employer: the declared holder has to match, otherwise the request is rejected without any useful explanation.
• Confusing a SIM swap with an operator change. Replacing a SIM with the same operator does not touch the number and triggers no port.
• Signing elsewhere without pricing the handset balance. The article on mobile plans with or without a contract sets out why those two lines of the contract are not terminated the same way.

One last point, whichever operator you join. Only four players run their own mobile network in Belgium: Proximus, Orange Belgium, Telenet with BASE, and DIGI. Every other brand rents one of those four networks. The porting procedure, though, is identical with all of them, incumbents and virtual operators alike: it is law, not commercial policy.

Sources

• BIPT, number portability and the Royal Decree of 2 July 2013, consulted on 28 August 2026.
• BIPT, Easy Switch frequently asked questions, consulted on 28 August 2026.
• Telecommunications Ombudsman Service, scope and cost-free remedy for the consumer, consulted on 28 August 2026.
• General and specific terms published by Belgian operators, surveyed on 28 August 2026. Items that are not published are flagged as such in the table.