I received a post message today, saying what your last number is and what your balance is. What does "cash" mean here %B

The short message you received is a current account change notification service automatically added by the postal system for you. The first month is free, and 3 yuan is deducted from your account every month, and 30 yuan is deducted every year. If you don't want this service, just call 1 1 185 to cancel. You can provide a complete account number, card account name, and the mobile phone number of the received text message when you cancel. . When the SMS service is cancelled successfully, the customer will be notified by SMS.