After Samsung n9002 changed its mobile 4g card, the SMS can't be sent, the phone can't be answered, and it can't be dialed.

1 used to change cards. Can you take out the SIM card and put it on other mobile phones?

2 environmental factors, when the cell phone signal is bad or there is no signal.

3. Take out the SIM card and wipe it with a little alcohol, then put it in the card to test whether it is ok.

4 Call the operator's customer service phone to see if the number of the SMS center is correct in this area.

5 Check whether the mobile phone is equipped with security guards or third-party SMS software, and test it after uninstalling.

6 mobile phone hardware problems.

In the sixth case, it is recommended to go to the factory direct sales engineer for inspection and maintenance.