I had a guy once buy a gun from me on gunbroker, paid by credit card. Everything went through, I shipped it to his FFL and he picked it up
A week later I got a chargeback (i.e. he disputed the charge). I looked him up and called him and asked him what the problem was. He was an elderly guy, and said he didn't recognize the charge. I explain to him what the problem was and told him he needed to call his credit card company and tell them it was a mistake. As of a week later there was no change. I called him back and I asked him again what the problem was, and he said he called his credit card company and they said that he couldn't change anything since he has already started the dispute.
I sent him a letter by registered mail explaining that if I didn't have a money order or certified check in 7 days I was going to call the sheriff and file charges. Then he called me, wanted to know what the problem was. I told him he had 7 days to send me my money, which included a service fee for all my lost time and fees for the charge back.
He sent me a money order.