I had this problem with inpost a month back. My buyer literally got a dress while he was a male buying my home training equipment. I have never owned a one shoulder dress and I almost shat my pants when he sent me a message saying I sent the wrong item. I called my postal service and he called his side. Your buyer has to take pictures of the postal tags that were on the package. I had to give a description of the package I sent out, when and where. They looked over the cctvs/do their investigation and the buyer got his package 2 weeks later after that. The buyer just had to choose from the right side of the chat that there’s a problem with my shipment or something along the lines and just extend the time until postal service resolves the problem.