When applying for a credit card, in addition to the personal mobile phone number and fixed phone number, it is also necessary to reserve the mobile phone numbers of friends and relatives. When the bank can't contact the cardholder, the bank can contact the cardholder through the mobile phone number reserved by relatives and friends, so the bank can't contact the person who handles the credit card to call the person who left the phone number in order to get in touch. Banks are financial institutions established in accordance with the law to operate monetary credit business, and they are the products of the development of commodity monetary economy to a certain stage. Banks are one of the financial institutions. Banks are divided into central banks, policy banks, commercial banks, franchised institutions, investment banks and the World Bank, with different responsibilities.