EXTREMELY BAD SERVICE , PRIVATE BANKING OR NOT ALL THE SAME WITH FNB

i am very unhappy, since the 3rd of September I have been communicating with FnB regarding my loan. FnB debited my account on the 3rd September an amount of R3742 on my account for no reason. I cannot reverse this debit and no one can help me. I used the App, i used telephone banking and the private banking. There is just no service. I HATE fnb as now I am totally inconvenienced for the month