Debit order isssues

I have a credit life policy with FNB. I called their call center change banking account and move all debit orders to nedbank. In addition I told them that the debit order date should be the 26th but no for this *** the debit randomly anytime from the FNB account I am in the process of closing because of bad service after 20 yrs of being their customer. I noticed bank acharges and double premiums, why?