12, there is a problem with swiping the card at home appliances or large shopping malls. For example, the jewelry store pos machine jumps the code, and the acquiring company jumps the code to the gas station or restaurant. It's hard to control without your knowledge. It is suggested to make small transactions and credit card transactions 1000. 4. It is obviously abnormal to swipe your card for a long time in the same merchant or pos machine or swipe your card for a long time in a merchant or fixed merchant pos machine, and there is only one code for the acquiring institution. If the business transaction volume is too large, the system will automatically refuse. If a normal merchant has about 100 transactions a day, of which 20 transactions are cash payment, 20 transactions are online payment and 20 transactions are credit card payment. It is impossible for these 20 credit card transactions to have only one bank's credit card. If some sensitive bank credit card transactions are larger than the number of merchant transactions identified by the system, a prompt will appear. Merchants on the bank blacklist All banks will count their own "blacklisted" merchants. Merchants who have entered this list should not use credit cards. Needless to say, they are easily controlled by the wind, and there is no score.