Hi Holy.
The only problem is, how can we trust the casino's words?
I know the rules are the rules but who is checking if the casino that made the rules is playing by them?
If I was OP I would try to get a 3rd party mediator involved.
In case the casino denies that it pretty much shows that not everything might be as they are saying.
I'm not taking sides here, I just don't trust sites that make accusations just to not pay players. They took his deposit, they took his action. If he lost there would be no issue. It only came because he won some money. If everything is as they say they could share it with a mediation site, just OP needs to ask them to do so.
In these cases it's always statement against statement. Without seeing evidence it's hard to trust the casino. They make the accusation, OP's words here are just a result of that. So they need to show proof. OP cannot proof he doesn't own multiple accounts or what not. They are holding all the evidence.
Like I said, get a 3rd party involved, thats the easiest way.
OP seemed to be reluctant to involve an arbitrator to handle his case and verify evidence. If we want to get further insight on this case [aside from OP going with lawsuit] I think we can do what
Mahdirakib suggested, by either party providing the bet history, so we can see if OP indeed abused a minimal risk bet or not.
OP had actually gave his activity history
here, but it didn't give enough information on who he put his bets on. So maybe a betting history would help us advancing.