@whatever61 While waiting for an official answer from a Proximus moderator here, I will give you all the following::

If your mobile phone has been stolen or lost, we Proximus need to know whether you have a subscription through your employer.
If it is through your employer, also report this to the administrator in your company.
 

First contact Proximus customer service on the free number (0800/22 800, option 2) (or via your trusted contact  ).
Before you do this, call your mobile a few times and write down the date and times.
Proximus immediately blocks your SIM card for a maximum of 3 months.
If you have a Pay&Go card, Proximus cannot block it, but they can disconnect your name from it.
To also block or unblock your mobile phone, you need the serial number (IMEI code) of your device.
If you have not noted this, you will only find it on the proof of purchase of your device.
If you have not received this, please contact the seller of the device. You must provide this with proof of purchase.

how do i unblock my esim

If you already have a new (e)SIM card, you can continue to use it.
If you don't have a new (e)SIM card yet, you can continue to use the old one.

Have you asked Proximus to block your mobile phone?
To unblock it, follow these steps:

You need proof of purchase for your device.
If you have not received this, please contact the seller of the device.
You must provide this with proof of purchase.
Send a copy of your proof of purchase (where the serial number or IMEI code of your device is visible)
and a copy of your identity document to ccj@proximus.com.
Your request will be processed by them as soon as possible.
You can ONLY request to 'unblock' your device at this e-mail address.

Thanks for trying to help, Martin :)

Unfortunately, it doesn’t answer my question.. I don’t need to block my line, I just want to know how is the activation process on the new phone.

Usually, as with other eSims I will just login to my account and activate it on the new phone and this will automatically deactivate it on the old phone as well.

But maybe Proximus has some more complicated process, like sending me the eSim activation code by post or something like that..

meanwhile I'll give you some info, which I found on the PX site :-)

Activate and use your eSIM | Proximus
 

Awaiting a response from a Proximus employee (moderator) on this public forum

Activate and use your eSIM | Proximus

= You can transfer your e-sim between smartphone X and Y with your QR-code (normally available via your MyProximus account)

but in case your smartphone was stolen or lost normally you should take steps to block your smartphone lost (IMEI nr) and your (e-)SIM nr 

= Your mobile nr should be associated to another new (e-)sim nr

&

maybe/probably webshop will not sent (e-)sim abroad 

Thanks guys, it seems to be the answer that I have to first block the sim and then get a new one with the same number. 

Unfortunately, in any case I will have to get something physically to activate the esim in case of phone loss. 

I was hoping for a complete online solution..