Credit card dispute

I had an debit order from geeker.com going of every month. I never authorised this. Card disputes say I dont have a case and that I should cancel directly with merchant. I tried that but according to their system I am not registered. I lost more than R2000 so far. And No one can solve this issue and stop the debit order. It is not the first time I had issues with Nedbank. I am really fed up. After 10 years I think maybe it is time to change banks.