Why can't Li Jing's mobile phone send or receive short messages?

What should I do if my mobile phone can't send short messages? Can be ruled out in the following ways:

1, confirm whether the SMS service number is accurate, such as: SMS → More → Settings → SMS Service Center → Set it as the local accurate SMS center number (consult the network operator);

2. Restart the phone;

3. replace the SIM card;

4. Back up important data and restore factory settings;

5. Bring the purchase invoice and warranty card to the mobile phone for after-sales treatment.