Bullying, Threatening Telkom debt collectors

It seems the lovely bullying Telkom is back to harassing my elderly mom about an account that was cancelled with them multiple times since 2015. What's next someone knocking on the door to break her knees? I have emailed, online cancelled, facebook, hellopeter, all avenues available to us. What will it take to get Telkom to stop bullying and threatening people when the problem obviously lies internally with Telkom?