No help from cell c

I had a contract with cell c 99 a month. When I was sold the contract I was told it's 99. In Dec I enquired about ending it the agent at the call centre to ask how much i owe tp close it. She said it was paid and i can use it for dec. Then i got cut off a week later and told i owe 99 more.She said some1 will call me to upgrade if I want too. I then get told i owe huge amounts because the agent I spoke to failed to tell me the premium will change to something called old billing without a discount. No one informed me. I have made inquiries and no one wants to help me. The keep insisting I pay. I dont mind paying the 99 i owe per month if u insist i pay but jot whatever amount suits u with no agreement. Worst service ever. Now I wouldn't even stay if it was free.