Dispute from a buyer

[mrfoton]

Hello, today i receive my first dispute from a buyer and I dont know what to do.
I Do the same thing that I always do in that Gig, and i try to ask them what its wrong but he only answer to me “refund”, “i want my money back”

What i should do in this case?

[rayhanoficials]

Better, contact helpline with your proof