Why can't a bank card cancel SMS notification?

(China Merchants Bank) If the SMS notification service of 3 yuan/Monthly has been launched, it can be cancelled in the following ways: ① Popular version: Please log in to our home page, click the popular version of personal banking on the right, enter the card number and inquiry password, then log in, click Account Management-SMS Service of China Merchants Bank in the horizontal menu, and click "Function Off" under the "Operation" column to cancel. ② Professional Edition: Please log in to the Professional Edition, click on "All-in-One Card"-"Account Management"-"China Merchants Bank SMS Service", and click "Function Off" under the "Operation" column to cancel. ③ Mobile Banking: Please log in to the mobile banking, click the menu "Account Management"-"SMS Service of China Merchants Bank", click "Function Off" on the opened page, and follow the prompts. Tips: If 3 yuan/Monthly SMS notification service is not enabled, that is, your account is the default free notification service, you can't cancel it directly. You can change the mobile phone number of the notification to an invalid number.