Cancelling of contract

I have tried several times to cancel my contract with Telkom SA since last year November. My contract expired in December last year and i am still being billed for a contract that I do not use. And i am being billed more than what the contract amount was for initially. I have been to the N1 City branch several times for assistance and i was told that somebody would call me and to this day I have not received a call. I was told that because i was called thrice the contract was not cancelled. I am a single working mom and have two other contracts with Telkom and I cannot afford to be paying for a contract that i do not use. I will not recommend Telkom to anybody. They have good deals but their customer service is absolutely pathetic.