ABSA will not refund money paid into their account

It is amazing how quickly ABSA is to climb on the phone and threaten me with legal action when I originally contacted them for assistance. Having no other option, I went onto debt review. I have paid ABSA all the money I owe them. In error, Nedbank, paid an amount into my old ABSA cheque account. It is only R300.00. I could close my ABSA Credit Card over the phone. No problem. I cannot close my cheque account telephonically and I am told I have to go to the branch to close the account and apply for a refund of money NOT EVEN DUE TO ABSA. This if after they have charged me fees for the money being paid into their account. This is not my fault. I don't owe ABSA anything. I have paid off everything I owe them. I did not run away and avoid my responsibilities but the cannot refund my money? They owe me money. In this day and age you can be threatened telephonically day in and day out with legal action but you cannot get a refund of money not even due to them.