Credit card consumption is generally based on password and signature, or without password, by signature. If the merchant thinks it is necessary, you need to show relevant certificates. When spending, enter the password if you have it, and press the Enter key directly if you don't have it. Then sign the bill.

If you lose it, call the bank customer service as soon as possible to report the loss. Many banks have exemption clauses for stealing credit cards 24-48 hours before reporting the loss. (depending on the type of bank and credit card)