What is the short message service of postal savings? I don't understand at all. Urgent!

Postal savings SMS service is to add SMS notification to your current account. When your account changes, such as withdrawing money, saving money and transferring money, you will be notified by SMS. The monthly SMS usage fee is 2 yuan, which will be deducted. In this case, you may have left your phone number when saving money, so you can do it yourself, or you may have left the wrong phone number and you can't receive the text message yourself.