NKB Nedbank deduction

Last year I had the exactly the same deduction problem for about 2 years! A NKB (fee for internet services) that I did not authorize, started again deducting monthly fees. It started with R33.50 and then chanced for the last 2 months to R201.00. At the Branch I was told that if I stop/call back the debit order they will just do as above and change the debit amount. The branch cannot stop it or pay it back, the Call Centers make promises and eventually revere you back to the branch? How is this possible that a unauthorized deduction can just be done?