Dear

When I attempted to utilize my [firm] charge
card for a purchase on [date] , I was informed
that I would have to speak to the credit office before
I could charge any additional purchases to my account.
Inasmuch as there were several customers waiting in
line in your credit office, I am writing to you instead.

Could you please tell me if there is a problem with my
account, and, if so, the nature of the problem?

I will be looking forward to your prompt reply.