Please can someone advise an ombudsman or have advise what I can do? Telkom is not responding or doing anything about my complaint.

I have been emailing and phoning Telkom to try and sort this out. This is affecting my credit record. I am so angry right now. I asked for Telkom to cancel my contract on the 2nd of July for the end of October when my contact ended. I have proof of this cancellation. Telkom doesn't do anything. I get a message saying sorry I have to pay they can't reverse this. But the contact is cancelled now. This is absolutely ridiculous. They can cancel it now within a day???? I have phoned and emailed and nothing is done about this. I haven't had a response to this message. Please can someone advise an ombudsman? Or another way forward to sort this out.