I simply CAN NOT get assistance in changing my VOX debit order details

Vox, I have been trying very unsuccessfully to get my banking details for my debit order with your organization changed, so that the next debit goes off my new bank which is where my salary will be come 1 Oct. Your contact center keeps referring me to make the change on your portal, despite me advising them that your portal simply DOES NOT ALLOW one to edit the bank account number, you can edit to put in your new bank name but that is the full effect of the changes you can make via self service. I have emailed your accounts department, your debtors department your debit order team, asking for assistance in making the change. And all I get is your customer service team pointing me BACK TO AN INEFFECTIVE self service portal that DOES NOT allow the bank details to be changed. The only other thing I see is canceling my Vox services and changing providers, so that I can have them debit my CORRECT bank.