DEBIT ORDER GOING OFF

I changed my banking details with Bonitas after consulting with them about the procedure first. I was told to make a cash/EFT payment because the debit order instructions were sent out already and after completing and sending through the documentation to change my banking details, it will take 3 to 5 working days to take effect. I did an EFT last weekend and sent through proof hereof to Bonitas and requesting that they confirm that this was in order. However, this morning I received a sms to notify me that my debit order for Bonitas went through and I had no communication from them to this effect. This caused my banking account to go into arrears! This is not acceptable. They informed me that it was too late and that I had to make a separate payment. Who will now take responsibility for the fine I will have to pay at the bank for being overdrawn and when can I now expect my money to be paid back? They surely need to inform their consultants giving out information what the correct procedure is!