Poor Service by Standard Bank.

I have a home loan account with standard bank. They normally debit on my account around 25th of every month. But this month in February they made a double debit on my account. I called their call centre and ask them to reverse the payment because my account is not in arrears, I was told that I need to write a letter requesting for the reversal of the debit order as if this is my mistake. I'm really disappointed in Standard Bank the way they handle issues.