I bet you 50 euros that I could pay a random homeless person or drug addict to go buy a basic android phone with SIM card and service at retail. The sort of people who are running drug smuggling and middle/end-retail distribution operations have access to lots of such persons.

'smurfing' methodologies are well known.

They can steal a SIM, or buy one from a country where they are available freely.

Belgium is one of these countries.

Are you a member of an organized crime syndicate?

Oh I totally agree, I think the phone-number requirement is absolutely ridiculous. Just pointing out that it's possible.