Call the number on the back of your American Express credit card. Select the option to speak to a representative when prompted.
Inform the representative that you are contesting the charge.
Provide the representative with the charge name and the actual price debited, as well as any other information requested. The representative will have an envelope containing the official dispute forms sent to you.
Fill out the forms mailed to you and send them back. The form typically requires your name, address, social security number and card number, as well as the charge and price being disputed. Be sure to include any evidence, such as notes, receipts, transcriptions of conversations, or statements.
If your card is registered online, you can also dispute a charge via the American Express website (see link in Resources). Type "dispute a charge" into the "Search" box on the home page, hit "Enter," then click "How do I dispute a merchant charge?" under the FAQ section.