He thought he could totally treat the seller as an idiot.
Item has problem，he contacted seller，seller work out a Partial refund solution，he agreed，seller refund him the agreement amount.
After he got the money,he immediately contact seller saying he want more refund,if seller not do that,he will open case and negative feedback. The seller is willing to refund him more money. He once again agreed，and got the money，
After he got the money，he wants to play the trick again.
Such dishonest buyer.