He buys only from listings that feature an option to have a code sent to him for mobile top-up cards, gift certificates, etc. He then files a dispute with his bank, uses the code, and after 5 months the bank finally went in my favor. Luckily, I used the code before he could do any more damage.

DO NOT give an option to send the card code over email. You more than likely will be scammed and it isn't going to go in your favor at first. It's best to list a gift card/phone card as mail delivery only, with delivery confirmation.

2 other sellers confirmed they had this happen to them in dealing with this particular buyer.