Final answer:
The first action you should take if your credit card is lost or stolen is to call the card issuer to report the card lost or stolen.
Step-by-step explanation:
The first action you should take if your credit card is lost or stolen is to call the card issuer to report the card lost or stolen. This is important because by contacting the card issuer, you can prevent any unauthorized purchases or transactions from being made on your card. The card issuer will then cancel the card and issue you a new one to protect your account.