NO JOY WITH DEBIT ORDER SWITCH

I have been struggling with Toyota for the past 3 months to switch our banking details as we had changed banks. I had made contact with 4 different consultant at TFS was sent a bunch of document to fill in and return all of this for just a simple debit order change which was from Nedbank to FNB. After submitting all these documents still no joy Toyota is still debiting from our nedbank account which has no funds in it. This is so annoying and frustrating to say the least the service is pathetic and has gone to the dogs.