Contact the seller & explain what you INTEND doing if he / she does not refund you fully, tell them you intend adding to their feedback what you think of the seller, if that does not work go back to your Feedback section & state what the seller has done, if they have good feedback this should damage their reputation, Pay pal only gets involved if the goods have not been received or you are waiting for payment. EBay is the avenue for this problem, had something similar but I sorted it.