damaged battery

i bought a car battery in May within six weeks the battery stopped working. i went to have a battery replaced instead they loan me a s****ped battery and was told to come back after 3 days. i was specific i dont want the same battery anymore i rather exchange for a new battery. when returning after 3 days they refuse to give me a new battery and add only 100 rand now it was an issue of they want an invoice of which they didn't request when i went to lodge a complain. i paid using my account and showed them a slip on my phone as proof, but they refuse saying they want hard copy. i spend so much already on transport and have mechanic to determine what's wrong with my car and transport to battery centre only to be told its just a new battery purchased which was supposed to last me 25 months. should they refuse to give me my money which means someone *****ulently bought in their store with my card. if anyone is using them, they should be aware of their customer service.