FNB refusing to close off my paid credit Card

Honestly really sick tired of the run around FNB is giving me. I paid off my credit card in August already and I receiced confirmation from the credit card department, someone called Prudence Mathebula. This was her message in the email "We hereby confirm that your account has been closed in accordance with your instructions". Thereafter the credit card account was removed from my App. Now today, months later, this credit card has reappeared on my account with a negative balance of R100 called small balance write off! What on earth is that? Why now?! FNB is honestly ridiculous. Really regretting banking here to be honest. I can't deal with this run around. Please sort this mess out. This credit card account was actually meant to be out of my ITC already and here you are making unnecessary money demands! Its ridiculous!!!