Xiaomi 4C can receive short messages but can't send them.

1. Signal reason

2. Owe the phone bill

3. SMS center numbers are inconsistent

4. Manage applications-all address books, and clear cache and data.

5. The address book/contact person is prohibited from starting.

6. Remove the battery and restart it.

7. Put the SIM card on another mobile phone for testing.

8. Use third-party communication software

9. Restore factory settings

10. Brush the machine, preferably with the official ROM.

PS。 Just because a contact can't be sent out, don't bother. Call him later or contact him online. (The possible reason is that the other party's short message is full or the signal is weak. )

The above is for reference.