Quoted from LTG:No idea what the scam is.
Probably a variation of an overpayment scam.
Someone sends you money you don't expect. The scammer demands a refund from you. Then after you send the "refund" as a separate transaction, the scammer reports the original transaction as fraud or whatever and gets it reversed.
So, you're out both the money from the original transaction, as well as the "refund" you initiated from your end.