Android - How to prevent phone operator from opening spam popups?

This generally seems to be done as a 'value added service' in the Andriod SIM Toolkit, as per this question here.

However, in this case it may be a Cell Broadcast.

Cell Broadcast is designed for simultaneous delivery to multiple users in a specified area. Whereas the Short Message Service-Point to Point (SMS-PP) is a one-to-one and one-to-a-few service (requires multiple SMS messages, as each message can only carry one phone number), Cell Broadcast is a one-to-many geographically focused messaging service. Cell Broadcast messaging is also supported by UMTS.

If you go to your SMS app and go SMS > Settings > Cell Broadcast and disable it, this should stop this popup.

If that can help someone, the app I needed to disable was /system/app/Stk.apk and it was called "Services SFR v4.1.2-LL__zg".

Try looking in Settings -> Apps -> swipe to the right until you get to the "all" tab, and then scroll down until you see "SIM Toolkit", at which point you should be able to tap on it, force stop it and disable it.