Extra money paying for my contract.

They are charging me other things to the contract I am having with them, when I ask them about the Chargers no one can give me the feedback the money is for what. I am paying R442 for my contract with extra R593. This R593 I don't know is for what. The other contact , they are charging me for two handset that I don't even have, I returned back the handset but they are still charging me for it. I have a proof they received the handset. I am paying R338:for something that I don't have. I calling them every month about the issue but I cannot get any assistance.