Account Closed but Debit Order still goes off

On the 10th December I received a call from MFC informing me about an early debit order as its the festive season. I informed the lady I spoke to that I have just sold my car and that they should not debit my account as the car is sold. She clearly ignored this as when I check my bank statement an unsuccessful attempt to deduct R 6000 from my account on the 11th. On the 28th December the debit order came off. I called in and spoke to a lady by the name of Thelma. She confirmed to me that the account was closed on the 14th December already. 14 days prior to the debit order going off on the 28th? What is happening, do you not have people that check this? I would like my refund and ASAP! Is MFC going to be held liable for all my debit orders that bounce back? Will they incur the charges of this?