I can back from China, I did not change any thing in my phone setting. Then I can not send/receive messages to someone, but can send/receive from other person. What should I do to resolve it?
Welcome to the community
A quick test to verify if your service is working as intended is to send a text message to your own number. Though, you've mentioned that you're unable to communicate with someone by text. Just to confirm, does it impact only one of your contacts? If that is the case, is your contact able to send/receive texts with other mobile users?
Also, what about your ability to call and use mobile data, are these features fully functional on your line? Let us know!