According to the text this should affect only people who pay by direct credit (where you enter the bank account number every time you pay). If you use credit card, direct debit or bill payments setup by your bank then it shouldn't be a problem.
I have just paid using the existing payee in my list, provided by BNZ... After paying I thought it would be good to check, and sure enough the bank account is the old one.
Because I added this payee years ago I don't remember if this was manually created or selected from the BNZ list. I'd say the first one.
So even if you pay by bill payment setup make sure to check the bank account.
I hope my payment is still collected by WorldxChange this month...