Unable to cancel my contract as per agreement

I have a contract with Cell C from 10th October 2013 to 10th October 2015, I called in a month or so ago to have it terminated after my last instalment which was this month, to my surprise when i called in two days ago that it was not terminated and i was told told i have to wait another 30 days and pay again next month, i find that unfair since i have done my part and called in on time it is not my fault that staff there are *********** that don't do their job well. i refuse to pay again and want that contact terminated NOW, I don't owe this people a cent , i have not missed a payment in the whole two years therefore i refuse to be treated like this, this is a violation of my rights, Malapane confirmed that i spoke to 4 staff there and i had the same conversation with the 4 of them and not even once i requested for a cancellation, now is it possible for a person to have a same conversation with 4 people?I need that contract terminated NOW,