About a year ago I had a $3800 balance on my Amex card, but had an $8500 limit. They dropped my limit to $4000 for no reason and I didn't get the letter from them until 3 days after it happened. Fortunately I logged into my account the same day they dropped it, so I didn't charge anything. But I'm sure that if I had charged $200 in those 3 days and gone over the limit they would have charged me an over-the-limit fee.