Trying to change debit orders as i have changed banks.

I have recently moved banks from ABSA to FNB and now i am struggling to update my banking details, this is a joint bond. What confuses me is that the consultant told me that they cant amend my debit order on their system and that the full amount will be deducted from my new account. I am baffled about the level of incompetence over such a small issue.