Worst Service ever!!!

I bought a few items on credit at the above store, specifically the one in Palm Springs Orange Farm. One of the Items purchased was a Television. When the items were delivered, the tv didnt have a box, a manual or even a remote. This was in April, i went back to the store and told them i didnt want that tv and requested a new one. They since havent replaced my tv but are demanding me to pay for it. How can i pay for something i dont have?? I have tried to ask them this numerous times but they have now put lawyers on me. Who are also now demanding me to pay. They have tripled my installment from R783 monthly to R2500 monthly without my approval. Ever since i returned the tv no one at the store is calling me to tell me whats happening with the tv i initially purchased instead they give me attitude telling me how much i undermined them by bringing back the tv. What exactly am i paying for if i dont have the tv???