Telkom: The communications giant that does NOT communicate

I app**** for a service which was confirmed, cancelled without my knowledge, then the deal changed and the price doubled. What was sold was not what was received and despite having cancelled the deal within the cooling off period I continue to receive accounts. I spent literally hours on the phone (not a Telkom one because that never materialised) with call centre staff that are not able to take decisions. Despite having written, phoned, communicated on their "online chat" service to date, some 4 months later, not a single request to speak to a manager of some kind has been forthcoming. I have sent a paper trail of daily emails that remain unanswered despite begging, pleading, shouting, etc. One or two employees rang me - requested the same documentation that was requested initially - with still no resolution. One cannot obtain a Snr Manager's detail, telephone number or email address. So, how does one resolve a basic query? A massive paper trail of daily communication to Telkom is available despite which they continue to disregard a basic request. So here's a simple question, what does one do to rid oneself of a non-responsive supplier? Visits to branches were also unsuccessful, only the call centre can help. However the call centre is an outsource company which absolutely no interest other than making bogus sales!