Merchants should establish procedures for responding to suspicious transactions. Your sales staff should be familiar with these procedures and receive regular training on them.
If your sales staff is suspicious of fraud, they should follow the established procedures, which could include asking for identification in accordance with the following rule:
A merchant may request cardholder identification in a face-to-face environment. If the name on the identification does not match the name on the card, the merchant may decide whether to accept the card. If the cardholder does not have or is unwilling to present cardholder identification, the merchant must honor the card.