What must cardholders do in case of loss or theft of their card?

In the case of loss or theft of a card, it is essential for cardholders to report the incident immediately to customer service. This prompt action helps protect against unauthorized use of the card and minimizes potential financial liabilities. Reporting immediately allows customer service to take necessary measures such as temporarily suspending the card, issuing a replacement, and monitoring for any suspicious activity on the account. This proactive approach is critical in safeguarding both the cardholder’s and the organization's financial interests.

The other options do not emphasize the urgency and importance of immediate reporting, which is crucial in protecting against fraud and ensuring timely resolution. Reporting to a supervisor alone may delay the necessary actions that customer service can execute right away, ignoring the situation could lead to significant unauthorized charges, and waiting to see if the card will turn up risks further misuse of the card. Thus, contacting customer service directly is the appropriate and required response in such circumstances.