How to modify the password of Unicom number through SMS?

The method of using SMS to modify the password of mobile phone service is the same in different provinces in China. The method for Tianjin Unicom to modify the service password by SMS is to send the SMS "40 1" to 100 10 to modify the password and reply "MMXG# old password # new password". Sending and receiving text messages is free. The method of modifying the password of mobile phone service by SMS in other provinces depends on local conditions.