Debit order reversal

Good day. I have had nedbank debit me of an amount of 3998.68 and 300. 300 which arrangement was made for. I have contacted fnb since saturday to reverse my money but every consultant has given me a different story. Is this how my bank shud be. Fnb being my bank must be able to assist me being their client. All i want is the amount of 3998.68 to be reversed Asap.

Thanks