poor service and deducting more money

I was called by some lady last year, they introduced the netstar go n I accepted, then after a month I called to cancel their go which was supposed to be R50 n they assured me they cancelledit, from there they still deducted more than my R145 car tracker, they deducted R204 every month, I called them almost every month and they all tell me they cancelled the \GO"but still deduct more"