Unauthorized Debit Orders

I settled and closed my credit card about a month ago,yet Nedbank still debited an insane amount from my debit card for the credit card even after I received the closure confirmation.I called several times,and have them my reference number and they just keep saying they will refund ,but nothing,it's been close to a month and still no action from them.This has been a very huge inconvenience.I am done with this bank.