Bad Service

I bought a Cable for my phone on the 3rd August at MTN Jabulani Mall,returned the cable on the 1st September because it was broken.When I got there spoke to Tshepo who said that I broke it and I asked him how can i deliberately break the cable,then he said I must come Wednesday to speak to the Manager.Went on Wednesday the 4th spoke to Lesego the manager we went back and forth and he said I must leave the Cable he will speak with the supplier til today no feedback whatsoever. The cable broke with a month and they telling me I broke it ,bought it for R300.