What is the problem that the new PHS can't send short messages?

According to your description, I suggest you check the following steps:

1. It is recommended that you click SMS-Menu-Settings-Advanced Settings-SMS Center Number to reset.

I suggest you try to call a friend to see if you owe money.

3. I suggest you try to see if other cards inserted in Xiaomi's mobile phone can work normally.

4. If it still can't be solved, please back up the data, enter the recovery to clear the cache, user data and all data, and try not to recover the data and send SMS directly after entering the system.

5. If it still can't be solved, it's recommended to back up the data and try the latest development version.