Telkom fails again.

I have cancelled my 20meg line at Telkom because the speed averaged at about 7megs. This was done almost two months ago, yet I am still being billed. In 2016, I had a similar experience and paid the contract cancellation fee yet years later they contacted me for an outstanding amount due. I honestly don't know what to do anymore. Is it fair to pay for a service which has not been rendered? Does the Consumer Protection Act protect us in such cases? Annoyed and Disappointed.