Have you tried providing screenshot of your withdrawal history like I suggested above? Though it's a bit far fetched, probably analyzing a Blockchain flow is a bit... way above the capability of their support staff, and they handle the situation themselves instead of forwarding it to their Blockchain analyst. Providing a more direct evidence will probably help. It doesn't hurt to try, anyway.
They have completely blocked my account so I can’t do any screenshots. I’ve never made a withdrawal before they closed my account.
Sorry for being a bit unclear. I am referring to withdrawal page from your account on the exchange, where you send your fund to be deposited to the anonymous-casino. If they suspect you a double-spend, unless I'm wrong, there should be two withdrawals made from that exchange in a relatively short time.