Phone for a code; A code 10 allows you to call for an authorization without the client becoming suspicious. Phone and inform the operator that you have a code 10. You will be asked a series of “yes” and “no” questions. If something is amiss the authorization will be declined. The operator may request to speak with the cardholder to ask account information questions that only the true owner of the card would know. You may use a code 10 at anytime you feel that a transaction is not legitimate.