Keeping your phone number when you change operator
In Belgium you may keep your telephone number when you change operator, and the transfer itself is free. You request portability from the incoming operator when you order, never from the one you are leaving. A number that has already been cancelled cannot be recovered, which is why the order of operations decides the outcome.
Steps
Write down the number exactly as it is registered
Take the number from a recent invoice rather than from memory, in full national format. For a fixed line, check which numbers are actually on the contract: a household can hold a main number and secondary ones that are billed together but ported separately.
Identify the holder of the line
Portability is granted to the person or company named on the current contract. If the line is in a former flatmate's or an employer's name, the transfer will be refused. Have the holder changed first, or ask the holder to sign the request with you.
Ask for portability while ordering, not afterwards
State the numbers to be transferred at the moment you subscribe with the incoming operator, together with your customer number and, for a bundled fixed contract, the Easy Switch code. A request made after activation is a new request and often means a new number.
Keep the old SIM active until the transfer completes
Do not throw away or cut the old SIM card and do not stop paying the old subscription. The number only moves when the outgoing operator releases it; if the line is closed first, the number returns to the national pool and is gone.
Update everything that authenticates you by SMS
Once the number is live on the new SIM, check banking apps, government logins and two-factor codes. The number is unchanged, but some services bind to the SIM rather than the number and need to be re-enrolled after the swap.
Mobile, fixed and prepaid are three different cases
A mobile number ports across the whole country regardless of where you live, because mobile numbering is national. Nothing about your address affects the transfer, so a move and a port can be handled independently.
A fixed number is tied to a geographic zone. You can keep it when you change operator at the same address, but moving to a different zone generally means losing it. Newcomers are often surprised by this, and it is the main reason to think twice before printing a landline number on anything durable.
A prepaid number can also be ported, including onto a subscription. It has to be registered in your name first, which since the identification rules applies to every prepaid card sold in Belgium. An unregistered card cannot be transferred to anyone.
Why numbers are lost, and how to avoid it
Cancelling first. The single most common cause. Once the outgoing contract is closed, there is no line left to transfer from and the number is released for reuse. Always order the new service first.
A name mismatch. The incoming operator checks that the holder of the old line matches the person requesting the transfer. A misspelt surname, a maiden name or a company registration is enough to block it, and the check is automated.
Letting a prepaid card expire. Prepaid numbers are deactivated after a period without use or top-up. Recharge before you start the transfer if the card has been dormant.
Assuming a bundle moves as one. In a fixed and mobile bundle, each number needs to be listed. Operators transfer what is on the order form, not what you meant.
Timing and what happens on the day
For a mobile line the transfer is generally executed within a small number of working days and takes effect during a defined window, often early in the morning. You will see a short period where outgoing calls fail before the new SIM registers.
Do not travel abroad on the transfer day if you can avoid it. Roaming registration during the swap is the situation most likely to leave you without a working line for several hours.
If the port fails, the incoming operator must tell you why and can resubmit. If it stalls or the number is lost through an operator error, complain in writing and then bring the case to the independent telecom ombudsman, whose intervention is free for consumers.
Frequently asked questions
Is number portability free in Belgium?
Yes, the transfer of the number itself carries no charge for the consumer. Costs that can still apply are unrelated to the port: early termination compensation on a fixed-term contract, a SIM card fee, or activation charges from the incoming operator.
Can I keep my landline number if I move to another city?
Usually not. Belgian fixed numbers are attached to a geographic zone, so a move within the same zone normally preserves the number while a move to a different zone does not. Ask the incoming operator to check the zone before you order.
Can I port a Belgian number to a foreign operator?
No. Portability applies between operators inside Belgium only. If you are leaving the country and want to stay reachable on the number, keep a low-cost Belgian prepaid or subscription line alive rather than trying to transfer it abroad.
How do I port a number that is in someone else's name?
Have the contract holder transferred to your name with the current operator first, then request portability. Operators verify the holder identity automatically, and a request submitted by someone who is not on the contract is rejected without explanation.