Stitching coming loose and the erea Manger didn't want to assist me and I paid lots of money for the sneakers

I went to the V&A branch never been humiliated like I was today especially if that person is in management they should know better we were actually shouting at each other because he didn't want to listen to me and my son sneaker is only 5 months and the stitching is coming off and u had proof of payment. He said there is nothing he can do as the shoes were worn but I don't understand his point because we buy products to use them.