I called the number back as well and dialed "zero" for the account number lol. This has scam written all over it. How do I know? My credit has been hit hard during this economy and there is no way American Express would want a cardholder with my credit lol.
I got a call from this number on my work line. I dialed it back and confirmed it was American Express as well. I decided to call the number on the back of my card to confirm there were no problems with my accounts, so I'm guessing it was a marketing call.