Exactly. If OP can also prove this - especially with this amount in dispute - a visit to a lawyer is definitely advisable ... unless of course - as is almost always the case here in Scam Accusation - there are other reasons that would justify a ban. Unfortunately, this often starts with common multi-accounting.

So if you are sure OP that there can be no other reasons why Rollbit is blocking you, I would contact Rollbit again and ask for clarification, stating that you would otherwise hand the case over to a lawyer.