If, as they claim, Bet600 have paid these two withdrawals, then there should be a transaction number for each of them. Ask them for the transaction numbers and then follow these up with your card issuer or bank. If Bet600 won't provide you with these details, then I would take that as a pretty clear indication that the withdrawals have not been paid. There are other options open to you at that point, but you need to give Bet600 a chance to provide this information first.