Telkom bad service

I had a contract with telkom that ended in august 2017. They told me to submit a cancellations forms which I did and they send me an sms that shows that the contract will be cancelled. The Unfortunately part is that it was never cancelled and they continue to debit my account. I called them in September and they told me it was a mistake and it will be rectified and I received an email. But now it is still not cancelled. Yesterday I received an invoice that says that they will be debiting my account this month again. I do not understand if I am still paying for the contract that ended or for someone else's contact. I have paid for 3 months that I was not suppose to.