Unauthorized debit orders

I have complaint previously that fnb aloud a company named loan finders to take money from my account. I never gave this company authority to take money from my account. I have to reverse the money every time and costs me money. How can i keep it n trusting the bank that allows anyone to take money even when you did not sign any documents and they have been blocked from takeing money?if fnb keep on allowing this i will be forced to change banks even if it means changing my car payments and all my debit orders ti another bank