Extremely disappointed with ABSA credit card account closure process

I am writing to express disappointment with the way ABSA is has handled the closure of my credit card account. I went to the bank to request closure, and settled the outstanding amount. Almost 3 months later I am now receiving endless calls from the bank informing me that my credit card account is overdue. They even have the audacity to give a deadline to settle the amount, or they will negatively affect my credit score. This is unacceptable.