FNB opens my credit card a month after I close it and receive my closure letter.

They reopened my credit card after it was closed and said I owe them money. I’m currently banking with FNB and I closed my credit card in October and also received my closure letter from FNB. To my surprise come November I’m told I owe R2000 and my credit card account suddenly appears on my banking app now. I’m highly disappointed by how this bank works, I feel humiliated by how a certain gentleman called me and said “closure letter means nothing”🤣. I guess next month they will say I owe them something else as well.