Telkom is *********** in cancelling my account

I would like to formally complain about Telkom. After being a loyal customer for about 10 years I had to cancel the contract at the beginning of the year with the service supposed to end at end of Feb 2018. I duly sent the cancellation notice to the cancellations email that I was required to do with relevant notice period. Not only was the request not done I have been sent billing for a line I have not wanted, needed nor used for the last 6 months. I have sent numerous emails to just about every department I could get hold of. I eventually got hold of escalation emails and sent them requests to cancel the line and credit the on-going billing. Eventually someone responded who promised in writing that the account would be cancelled and the billing would be credited. It was not done as promised. Months later and after sending more emails it seems the account is no longer being billed. But no credit has been done for the incorrect billing. No one answers emails. There is no help from the relevant departments that are supposed to sort this out only empty promises. Who can I speak to to get this simple matter sorted out. I would recommend never to use Telkom. They are eager to sign you up but absolutely incapable of sorting out the simplest of tasks when it comes to cancellations or credits.