Cancellation of landline

Notice of cancellation was sent to Telkom on 25 January 2018. The correct process was followed and all applicable documents were sent. After several calls, the line is still active and I am still being billed for a service I am unable to use. I have made numerous follow ups, requested that the line be cancelled and that a credit be passed for the debits that were taken incorrectly. The agents at the call center are unable to assist and all they do is log one request after another.