Still billing dismantled service

I have cancelled my ADSL line in KZN on the 5th of May this year with reference ***A. Subsequent to this cancellation I have now received 3 bills, one that did not contain the dismantlement date meaning that the pro rata calculation was not done for the final month and 2 more bills for full months rental. After the bill that was issued in June I phoned the call centre again on 15 June, only to be told by the agent that she could not assist and that the team leader was on a call but would phone me back. This call was never received. Is there somebody that can resolve this matter?