What should I do if Xiaomi 2s shows that the sim card is not activated and I can't send and receive SMS?

This paper analyzes the reason why Xiaomi has automatic synchronization function, automatically synchronizes all messages and call records to a mobile phone number (specific sim card), and integrates the card with Xiaomi's account. The account only recognizes that card, and the activation message sent after the new card is replaced is also sent to that card, so the new card cannot be activated naturally.

It seems that the only way to solve this problem is to restore the factory settings, pay attention to backup when restoring, and do not delete the application data. But the system settings must be completely redone.