terrible service

I have been receiving the most terrible service from telkom mobile, they changed my contract without my knowledge and started billing me for data that I did not have an when I complained they opened a case and closed it without ever talking to me and still carried on debiting me for data that I don't known. Now I have 3 cases opened with telkom and they have blocked my services while I wait for them to attend to my case. it is their fault that the is no correct bill for me and they told me to wait for someone to get back to me since October, but what about my service that are suspended. I spoke to a manager by the name of Charmaine last Thursday but that did not help at all. Now I want to cancel my contract with telkom and they told me to go to the shop, I went last Thursday and they gave me a form to complete and email and when I call them today they tell me to open another case at the store! ! I mean and I have to go to work and I was at the store in Festival mall and they didn't tell me about opening a case when I want to cancel my contract