Unauthorized debit order from Nedbank.

I have received a debit order for my personal loan that I have with Nedbank which was not authorized and when I contacted them to enquire I was advised that I should wait for the debit order to go through and bounce if there are no sufficient funds, I find this business practice unprofessional and having a negative impact on customers bank profile. I was also told that I cant address the matter with the department that runs the debit orders,. and shockingly this is not the first incident of having them debit without arranging with me on the set amount.