Delayed closure to claim intetest

I am so annoyed with these guys. I called in on the 5th and requested a settlement amount on my credit card and for them to close it. Then an agent says they will email it to me, I then waited, only to be called by someone the next day trying to retain me, I still said I want to close the account.. Today, I get another call from another consultant trying to retain me but I stood my ground, then they also promised to send me a settlement letter.. mind you, there was only R209 I think and a couple of cents left pending transactions... Now, after today's call, they date the settlement letter as today, when I requested it on the 6th, and are asking over R315, claiming interest etc Why am I penalized for their lengthy process and attempts to get me to keep the card open???? This is ridiculous and unfair .. I am not happy at all