It is the seller's job to be "happy with the transaction" after receiving FULL PAYMENT from the buyer. At this point, the seller has made a profit. For that profit, it is his obligation to make the seller happy according to the terms of the agreement. In a few cases, it may be impossible to make the buyer happy. However, that is the RISK you take to make a PROFIT. Give the feedback immediately and trust the community. They will take care of you in the vast majority of cases and you'll be a better businessman for it.