Bad, Bad customer service - Telkom

Worst customer service ever. I have a contract with Telkom for more than 8 years and suddenly they reduced my benefits and increased my premium without any communication or prior warning. After numerous calls to the call centre and even visiting their Tygervally store, I still do not know why they have reduced my benefits and can still not resolve the query. Complaints and queries end up in a black hole - never to be found. I will never buy any other product from Telkom and will not recommend Telkom to any family or friends. Worst company to deal with. Which entity deals with mobile service in South Africa where one can lodge a complaint?