Return for damaged shoe

I bought a shoe on the 26 of october using my bank card . After wearing the 2 times, the belt broke .. i took it back instore so i can get something else since the shoe was clearly a damage .. they refused to help me since i lost the slip . I tried showing them bank statement as proof of purchase but still they were not willing to help. Saying that they have to have docket number before assisting me . Im not happy at all because i spent my money on someething that i really only for it to be a damage, now i cant even take it back as if its my fault. They didnt even want to look at shoe . Unwilling to assist. Im talking about Mr price oxford street