If you detect abuse on your American Express credit card -- whether the card was stolen, a merchant overcharged you, or the card numbers were used illegitimately -- you must report it to American Express immediately. American Express will place a hold on your card and begin an investigation into the alleged abuse. If your card is lost or stolen, American Express will cancel your card and mail you a new one at no charge.
Report it online
Go to www.americanexpress.com. Log in with your username and password. Alternatively, set up online access to your account if you have not already done so. You will need your credit card account number for this.
Click on the tab at the top right-hand side of the page that says "Contact Us."
Click on the blue link that says email us. Send a detailed account of the alleged abuse. Include dates, merchant names, amounts and all relevant details. Include a phone number so that American Express can contact you with questions.
Report it By Phone
Dial 1-800-528-4800. This number is available 24 hours a day. Have your account number ready when you call.
Verify your identity by listing your billing address, date of birth or other personal information.
Ask for a case identification number, or for an extension at which you can call back to speak with the specific people investigating your case.
Report it to non-American Express officials
File a police report. Call your local police station and tell the operator you have a non-emergency, then explain the alleged abuse. This will help with any insurance claims you may have to file. This will also help if the abuse damages your credit report and you need to contest that negative mark with the credit-rating agency. You do not need to file a police report about a merchant overcharge, but you should file a report if you think the abuse is intentional or criminal, such as a stolen card or identity theft.
Check your credit report at www.annualcreditreport.com. Wait at least two months to do this, so that any abuse will have time to get reported to the credit agencies.
Check your American Express statement to ensure that you have not accidentally been charged for the abuse or fraud.