$50 amazon.com Giftcard Used by buyer but claims he hasn't

Invite code: TJGA3D
I have sold a $50 amazon.com giftcard to someone and they opened a dispute a few minutes after redeeming it (I received an email saying that the giftcard was redeemed exactly 1 minute after the payment was finished processing). I tried to chat with him but it was going nowhere, so I submitted evidence. I even started to record my screen for all my other sales after that to show that all the codes I sell work and are not redeemed. I hope you can help me with this problem.


The listing: https://gameflip.com/exchange_seller/1ec742bb-7008-4f8b-be02-3746c200c8eb


Unfortunately I see this was rescinded. If you think this was unfair, plrase PM me so I see if I can do something about it.