Return denied with the purchase invoice

My boyfriend bought a hat for my birthday, and it is small, I asked him to return it and bring a bag instead. Guess what he was told ? he was told that they cannot return the hat for hygiene, was the hat dirty ? who told him that he can not return the hat ? that noted on the receipt ? and now I am sitting with a hat that I cant wear its not like the hat is dirty or we don't have a slip. I find that unaccepted.<br> What should I do with hat ?