Cell C Contract-Bad Service

I will never take a contract with Cell C. After my Mother has been with Cell C for so many years, I'm not impressed with their services. They disconnected my line because I was owing. I payed the amount and sent the proof of payment via email. Till today, my line has not been connected. My contract is due to finish, they do not want to allow me to cancel the contract for 2 years. They keep on telling me that I'm still owing a certain amount. When I want to pay the amount, they cannot give me the figures. I have taken a Vodacom Contract and I have never experienced such services.