Struggling to close paid up accounts

Why do i have problems trying to close my credit cards after i have paid them in full. I made contact with Nedbank on the 5th January 2023 to close my credit cards after i have paid them up. The lady assured me that everything was done on her side. I then called on Friday the 6th Jan to make sure that everything is still in order and everything will be closed. She also informed me that all is in order and it will be closed. I then check on my accounts today only to realize that they have now added over R400 finance charges on my one credit card after i have requested for closure also my one green back product was not closed as per the agent that i was chatting to. Why is it a problem to close this accounts with you? Whats going to happen to the charges added after i requested for closure. Because as per the agent i spoke to i was advised that all charges will be reversed. This is honestly the worst service ever!!!!!