Paid for the Account and was debited still

Saturday 27 July 2019, I couldn't pay Discovery Credit Card bill at the FNB ATMs as I normally did. I phoned Discovery Bank and they advised me to use Pick n Pay tills to pay, that was done and money reflected instantly. On 8 August 2019 still debited me for the full amount. It has been a hassle to get my money reversed. I was thinking of moving my portfolio from the other bank to Discovery Bank, I guess I will not be doing that anymore