I sold a suit and got a message to say that the jacket had arrived, but not the trousers. I definitely packed the trousers. They say that the packaging wasn't tampered with. I have asked for the weight of the jacket, which has come in more than the jacket and trousers combined. Now they want to return the jacket - the suit was over £200 brand new, I wore it once and stupidly by the looks sold it for £5. Is it my responsibility as the seller to claim for the missing item through Royal Mail? Do I just refund and be done with the refund case?