refusal to credit my defected watch

I had purchased a watch from the Chatsworth branch on the 15 of Feb this year and now the watch has changed colour from silver to Brown I went to the bluff store as that is the closest store to me but they couldn't assist me so I went to Chatsworth , the sales assistant checked on my account and said I should take something to the same value but the was nothing that I liked I told them to please credit my account I will go to another store but they refused to the manager was called and she was just as useless and gave me an excuse that the docket cannot be found as it is too long ago, I find it to be really frustrating to receive such bad service from a big company Like foschini and even after telling the manager that I will report it she ignored me