Verified answer

Do you mean you've lost your credit card and don't know who to call to report the loss?

Did it not occur to you to look at americanexpress.com to see what you should do?

Here's their FAQ. "How Do I Report a Lost Card?" is one of them:

http://www10.americanexpress.com/sif/cda/page/0,16...

OMG...I hope you don't mean you simply need the American Express phone number....obviously you have access to the internet! You should have grabbed the nearest phone and phone book or even an operator and called!