May be you can provide any proofs. Some screenshoots, transactions or anything else? Quite big exchange may be some mistake? What do you mean dont credit account?
I also think we need to have pictures of transactions as well as orders without seeing any signs. It is impossible to claim any basis as scams if there is no accurate evidence.
I think that the buy order/sell commands are too high so the orders have not made, so check the order you can see this has occurred.