Buyer opened dispute

I need help with dispute. Buyer is trying to scam me. He will get game for free and money back lol. He is proving me i gave wrong key but key is directly from ASUS ROG support. Screenshoted everything and he is still trying to prove he got the wrong key. He can always buy second account (share it to his friend so they play together) screenshot second account and keep proving i gave him delxue edition insted of ultimate.

My code: 3UF755

Need admin assistance asap.