Got my first unhappy buyer

Listed two short and top pj sets for £1, I always check my items thoroughly and make sure there’s no staining etc on my items both when listing and when sending off in case there’s any storage issues, these had be worn two or three times each before being put into a sealed box under my bed, then listed a week ago. I truly don’t understand this at all, I’ve got 5 star reviews because I’ve always been honest, kept my buyers updated, and most importantly always being honest, I gain nothing from this as all my items are £1-£3 including the few bundles I have. I refuse to pay shipping as I don’t feel there was an issue at all and no one else has ever had a problem, what would you do in this situation?