FNB is failing me as a customer

I didn't know it was so difficult for a customer to get a mere account settlement letter until I requested one from FNB. It's 6 days now of waiting for a letter I was promised to get within 24-48 hours, I'm extremely disappointed. Is it some rocket science for FNB to calculate how much a customer currently owes and put it in a letter and email it to the customer?. I really don't know anymore what to do after wasting so much money to make calls and emails that aren't productive. I need urgent help!, this is totally unacceptable!