Failer to close a contract

I signed up for a contract 3 years back and it ended on the 26 of June 2017,prior to the contract ending I received a call to notify me that my contract is ending soon and if I don’t wish to continue with it then I have to fill up a form of cancellation and email it. I did that a month before the contract ends and to my surprise when I called Telkom customer service I was told they haven’t received my cancellation form nor the email I have sent. I emailed them again in July but still nothing was done and in August I decided to go to Telkom in Brooklyn mall to try to understand why was my emails not received and not be assisted on time. The consultant helped to redo the cancellation form then he emailed it but there was no reply from them to tell me if it will be cancelled as soon as possible. Two weeks after I went back to the same consultant and I was furious to find out that they looked into my cancellation form in the first two weeks of September and didn’t bother to let me know . I then called the customer care to find out if it was cancelled and the lady said it has been cancelled but to my surprise it was not cancelled. My patience is running out and im not gonna be billed for a contract that has ended a few months ago because of your negligence. I have long requested that this contract to be cancelled and I will appreciate communication confirming that the cancellation has been effected, Will grant you 24hrs to respond.