1. Cardholder's overdue repayment: the bank will freeze the credit card to avoid further losses. In this case, the cardholder needs to pay off the arrears as soon as possible and apply to the bank for thawing.

2. Risk of credit card theft: The bank believes that there is a risk of credit card theft and will lock the credit card to protect the cardholder's account security. In this case, the cardholder needs to contact the bank to solve this matter.