What is the function of the mobile phone number in the telecom hang-up SMS account?

The function of the mobile phone number of the telecom hang-up SMS account is: when the user forgets the login password and dials the customer service phone to reset the password, the new password will be sent to the mobile phone number of the account through SMS, thus improving the security of the user system. When changing the package, you need to enter the verification code received by the account phone to verify the validity of the package change.