Obviously the screw up was on your side, now I don't know how you manage your withdrawals requests whether it is manual or automated but the thing is the user here has inputted the right withdrawal request with the right address. His payment request is for Bitcoin and you sent it in Litecoin and your first response to him is "we cannot fix this problem on our side", you are basically saying to him is "deal with it even though you didn't made any mistake". Please own your mistake as this user looks like a decent gambler trying to withdraw his winnings from your website.