Faulty Cellphone Sold to customer

My uncle asked that I assist him with resolving the matter as he is failing with the store. He bought a cellphone at Ackermans that was faulty so he returned it. Upon returning it he told them that he does not want the cellphone as it was already sold to him faulty but would want to get another phone even if he needs to top up. Unfortunately the staff at the store, Ackermans Dk Suare, has not been wanting to hear him and just keep telling that there is nothing they can do. Apparently the phone is back from being repaired however he does not want it as he does not trust that its okay anymore. His name is Dumisani Kenneth Kubeka ***) and has an account with the store.