Poor service, ludicrous charges and no help

I have had problems with Telkom's poor service since August last year when I subscribed to a promotion offering various internet speeds. Openserve installed a router then left me to connect to the internet. Eventually, after several hours I managed to speak to a lady who helped me with the connection. Next day I checked the speeds and they fell short of what was advertised. After several weeks of frustration with inadequate speeds I cancelled their services, disconnected their router and subscribed to another service provider. However, I have still had our bank account debited on a monthly basis. The latest insult was to receive a message to the effect of "exceeding the usage limit and to pay R1 543,30 to prevent interruption of service....." What sort of equipment does Telkom have that shows I have exceed usage when I have not used their service at all since October? Currently we have paid approximately R 2 650,00 for not using Telkom's services and trying to interact with a regional manager to sort out this problem is IMPOSSIBLE!!!! I have 117 pages of E-mails between myself and various representatives trying to resolve the whole mess. What does one do?