Payment methods can be changed though, use Skrill or Neteller for example. They should be available in the Netherlands.
Not sure why they close your account but online gambling is kind of a grey zone in the Netherlands afaik, bookies and casino’s might not want to take a chance on getting a fine or whatever.
Over here in Belgium we have our own gambling laws and commission making it impossible to play on the big name casino’s like Videoslots or Casumo. There’s 9 licenses out there for online casino’s which are all in use, all being tied to brick & mortar casino’s. The law even says that as a user you could get fined if they catch you playing on any unlicensed casino…