Refund ****, twice debited

I have a personal loan with Nedbank, firstly on the 28th of October 2020 they took money from my account an amount of R2800 and then again on the 2nd of November 2020 I got debited again with the same amount. So Nedbank debited me twice with R5700 and when I call for a refund its stated that I will get one of the amounts back in my account in 2 working days time. I call again on the 3rd working dy and now im told that the refund will not be proceed and I wont be getting a refund anymore. How is that possible? Its paid via debit order so there is no way I missed any payment. Nedbank is a **** of a bank.