Cancellation process for contract

I have a contract with Cell C which expired in January 2016. Months before the time they contacted me more than once to upgrade the contract. Every time they contact me I told them that the contract needs to be cancelled. Once when I was contacted they admitted that they could see a note on the system that it must be cancelled. Contract is still not cancelled and no one told me that I should phone the cancellations department. When I queried why I am still being debited only then was I told I have to contact the cancellations department. Contacted cancellations department who informs me that a 30 days notice period is applicable. REALLY????!!!! Month ago I told a representatives from Cell C that the contract must be cancelled and now I must pay another month for their incompetence? I requested that a Manager should override the 30 days notice period and I was told by the Agent that the Manager would tell me the same thing. Cell C is this really how you conduct business? I did not know I should contact a different department for cancellation and neither was I told by any of your staff who contacted me on various occasions.