Complaint about people not doing their job properly crs-

On the 22nd of December 2023 I went to FNB Westgate branch to close the credit card I had at the time and the lady that was helping me phoned credit card department and notified them they said it will be closed in 48 hours, she told me I had to settle the balance before it could be closed of which I did, I made a transfer of what I was owing while I was still at the bank. Getting home and knowing that I closed credit card I shredded the card and threw it since that time I haven't been using the account. To my surprise last week I got an sms that I'm owing credit card then I went back to ask they told me I used it for Buffalo payment of which I did not, my question is why did the account that shows on their system that there was a request for closing made in December remained open up to April and I used to get messages that I'm owing so much and expected to pay so much on a monthly basis but I have not been getting those messages I didn't even know how much was I owing but they told me they couldn't close it because it was still owing. I payed the money they said I was owing but I feel I've been reaped because of someone who did not do his/her job can a further investigation be made and the one who did not do his or her job pay my money back because if I was owing they should have notified me and the bank teller that was helping me to make me aware and none of that happened since December up to now why the silence???