Charge Back Policy On Private Load

Dear Fellows,

I got a private load from a person in a Greece. He have no account on payoneer he just process the private load after all verification with his credit card. Now after about one week. He ask me to do another work for free when i refused he said that he will ran a charge back over payoneer and I have to pay that amount back. So is that possible?
Please guide me if it is possible than I am not going to use payoneer again and I will with draw my money from the card so in case of charge back I will not pay anything. It's about 7 days after the transaction. I don't think so he can not claim charge back.

please guide me


Regards
M