Fyi

Proximus employees will not be online on this public forum till monday

However:

it is of course possible to port mobile numbers from operator X (Base) to Y (Proximus)

https://www.proximus.be/support/en/id_sfaqr_call_nb_port_new_network/personal/support/telephony/subscription-and-pay-and-go/change-your-price-plan/keep-mobile-number-when-becoming-customer.html#:~:text=Keep%20your%20mobile%20number%20when%20you%20become%20a%20customer,-Keep%20the%20number&text=If%20you%20order%20in%20a,if%20you%20had%20a%20subscription)

Customer number,(s) phone number(s) and sim card number(s) will have to be provided (maybe/probably a document to be signed) via private message to Proximus (not in public on the forum)

and it also is possible to move numbers from person A to B

https://www.proximus.be/support/en/id_sfaqr_take_over/personal/support/myproximus/move-change-or-cancel/change-your-contract/take-over-someone-else-s-number-tv-internet.html

the above document has to filled in and sent up signed by both persons involved

Hello @Nanda Pires,

First, I sent you by your email address the document to be completed and signed with both parties in order to change the holder of your account.

You can send it back to us at the email address indicated on this document.

Then, once the change of holder has been made, I invite you to contact our sales department on 0800 55 800

in order to import your two mobile numbers into your Proximus pack