These three prepaid GSM providers will not allow you service unless you have a bank account which you must use for the initial payment before activation:
- Mobile Vikings
- JIM Mobile (same ownership as Mobile Vikings)
- Scarlet
- (edit) Ello? They might have the same issue as the above three
At the same time, some banks will not allow you to open an account unless you provide to them a mobile phone number registered in your name with proof of that registration.
You open a “basic” bank account at a bank that offers those kind of accounts just for the one-time purpose of getting a sim chip from one of the 3 MVNOs, but Belgium has a separate rule that blocks basic accounts from receiving cash, even a small amount like €10.
So you must obtain a sim from a mobile carrier other than the three to get a normal bank account open which accepts cash. Then use that bank account to buy the Jim or Scarlet sim card. Then credit is trapped on the 1st sim card. You can do a phone number transfer to get it credited back, after they siphon off €5 for the porting effort.
I think Germany would work because I’ve heard their basic accounts allow cash deposits.
(edit) I was mainly just exposing the chicken-egg problem. But it’s worth considering the ethical consequences of supporting forced banking. It forces people to be dependant on a corporation whose objective is profit (not the well being of the consumer, most particularly with respect to unwarranted mass surveillance). That same dependency weakens national security. If Belgium were dragged into conflict with Russia, Russian hackers would DoS-attack banks. Belgium’s critical infrastructure (energy, water, healthcare, communication) is all becoming increasingly cashless and thus helpless in such a scenario. Vivaqua recently removed their cash machine and probably no one has noticed this.