You do realize that will accomplish absolutely nothing. There is no possible way the vendor can know if the card is stolen. If they knew it was stolen they would have blocked the card already. I mean it isn't like the vendor is sitting there knowing they have sold goods on a stolen card just waiting for someone to call in order to reverse the transaction.
the vendor can verify the CC's billing phone number and call the owner and ask him whether he authorized the charge. Fraud Prevention 101.
besides of that, the carder here is so stupid he even tells people which site he is carding on.