Say you order two (2) universal wall filter screens for $9@, but the seller sends you just one. You email the seller twice to report the problem, but get no response. Try to resolve the matter through eBay's resolution center--forgettaboutit! If you bought the stuff with a credit card, just ask your card to dispute the charge. If you bought the stuff through PayPal, just call PayPal (you will get the number and code on the PayPal website) and they will handle the dispute courteously and efficiently.