Debit order charges

I'm so disappointed with your homeloans department, they have changed my homeloan debit order without my consent. Our homeloan debit order was going off my wife account, she made arrangements with fnb to change to my bank account without my consent. My account was debited even though there were no funds. I tried calling department to find out and I was told my wife made changes however I was never informed about this. My account is in bad state as result , I just want to find out how do you allow something like that. So any one can phone and ask debit order to be updated to some1 bank account? No one is coming with straight answer.

Disappointed