formerly known as daveland
Join Date: Oct 2003
Location: NY, NY, USA
Programs: Hyatt Globalist, Marriott LTP, Delta Platinum, Hilton Honors Diamond, Wyndham Diamond
Posts: 2,969
You need to call Amex. They do not charge a fee for use of the card (other than the annual fee). They think you either were late with a payment or went over your limit - or used the card for a purchase from a company located outside the US. If none of these fit, there was an error but the only way you'll find out is by calling. If the error is on their end I am quite certain you'll have little trouble getting a credit for the charges.
One caveat - the one time I incurred an accidental interest charge, it was reversed, but the next month there was another one since the system thought I had a balance the last month. I had that reversed as well but had to realize what happened and phone the next month to have everything fully squared away.