Xiaomi 4 Unicom can't send out an error message 28

The reasons why mobile phones can't send short messages are as follows:

1. SMS service is not enabled on the mobile phone. You can contact the local manual customer service or activate this function in the local business hall.

2. If the SMS center number is not set or set incorrectly, just reset it;

3. The signal is weak, there is no signal or the battery of the mobile phone is insufficient, resulting in the information not being sent normally;

4. Because the system is busy, especially during the peak period of texting on holidays, it is suggested that you try again later or avoid the peak period of texting;

5. The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number;

6. SMS sending and retention is valid for 24 hours;

7. Whether the SMS inbox and sending box are full;

8. I suggest you restart your computer or change your mobile phone to test it.

In addition to the above simple troubleshooting, it still cannot be solved. You can contact the local manual customer service for processing.