Bond changed date without my authorisation

Am so disappointed with FNB home loans just changed your debit order date without your authorisation while you have signed debit form for the correct date. I was speaking to someone from the chat said if your account is on error they have a right to change the debit order date. But I said I have made arrangements already it was only R 2700.00 on errors. She said doesn't matter. So we need to be aware of this bank I can't wait to finished my bonds with them. I have been waiting for collection depart it is almost 20 minutes waiting