Nonsense service

I had a contract with cell c which expired on the 7th September. A few day after the 7th I received a call from one of the consultants who offered me an upgrade, whom I advised I am not interested and I would like the one which has expired to be canceled, which she rep**** "OK". To my surprise on the 22nd September I was billed 179.00 yet my original contract was for 20.19 monthly . I have called the contact care spoke to Mr L Govender who is a Team leader (Jhb head office). He advised that I should contact the billing department, the billing department is not able to help me. May someone who knows her/ his job function attend to this matter ASAP. I didn't agree to any new contract and it's really not fair that I should pay for something I have not authorise. The uploaded data, minutes and sms's are still available for your team to reverse. Kindly attend to this matter urgently. I am truly UNHAPPY WITH YOUR SERVICE!!!!!!!!!