Generally, you can issue a refund from their original payment (either in full or in part by entering a different refund amount before confirming), and while the 30c flat fee from PayPal isn't refunded, the 2.4% commission is, so a full refund will essentially cost you 30c. To get a refund of the FVF, you can send the buyer a mutual cancellation request, which they will have to agree to in order to get the credit. (If it is ignored, you can close the request yourself on the 8th day after opeing it and get the credit).
