Additional debit order charge

I am so unhappy with FNB, I have asked them to debit on the 27th of each month (email communication send to them) they still debit on the 25th as a result it incurs charges of R185 each month. I have told them numerous times of this as it needs to fixed for the 27th but no one has actioned this after 3 attempts. Its a policy I cannot just cancel so I am not sure do I continue getting charges of the R185 each month which they are not willing to pay me back. Its been a year they doing this still no resolution 185 x 10 equals to 1850 which they not willing to refund me back. What do I do. I really think of approaching the ombuds now. As I cannot also afford to cancel my policy I have had for more than 4 years already. What can honestly be so difficult in refunding me and debiting on the correct date.