I bought a top from eBay. Had a card through the letterbox saying my parcel was at the sorting office, the sender hadn’t put enough postage on it and there was £3.50 to pay. Collected parcel today and discovered that the seller had posted it as a large letter instead of a small parcel. I have asked her to refund me the £3.50 but she isn’t answering. Am I being unreasonable?