Car starter faulty

Hi, I had a good experience with the Supplier until I bought a brand new Car starter, I fitted the starter and it does not work properly. I then returned it and showed Proof of purchase but according to their policies on electronic items, they don't do exchanges or returns. That mean my money is in the drain. My question is, why does Shoprite and other retail outlets exchange electronic items if it does not work or break within a warranty. They should've been the same as I am a customer. What am I now going to do with a starter that doesn't work?