Fnb fix your debit order procedure leaving my account in a negative balance for a month

Why does my account show overdrawn with a negative balance of R111 there's a debt order that didn't go off I suspended the mandate yet its stll showing a negative balance for the debit order because my account has been tracked since the 4of September shouldn't the debit order have bounced in that time now I'm getting SMS because my account is overdrawn and I must make a deposit I can't pay for a debit order I don't want to go off that's been showing a negative balance since the 4th of September this should be fixed