3rd time this week being sold a redeemed gift card

Once again I have been sold a gift card and I go to redeem the code and it’s already redeemed. I have been refunded for the last 2 but it is a big hassle for me because I’m selling in-game currency which I generally make with loot boxes I buy using the PlayStation cards… I know the mods said buy from steam pumpkin and I don’t think I’ll be buying them from anyone else but him. Is there a way for Gameflip to monitor or middleman these transactions? I’ve started the dispute on the incident from today. So could you guys please check on the status of it.”UDUL53”