Bad service

I have a contract with Telkom for more than a year now and I have experienced bad service from the start. I have a hearing problem and I had completed a form advising that my friend can assist with communication between myself, her and telkom. They have been giving us so much problems with that arrangement that I had went to the store to talk to them face to face and still had problems with communication and they don't understand or try to understand my situation. Excluding that problem that I have overcome and gotten used to it but then the billing and debit order amounts that don't make sense. They have been overcharging me and when I pay full amount and the next month I still owe them an outrageous amount. My phone was ****** and I have completed and submitted the documents but ever since the last documentation submission I have not received any feedback at all. Its been more then 2 months already and I have not received any feedback or update. I want to cancel the contract