First, check whether the phone bill is sufficient or change a SIM card.
Second, the number of the SMS center is wrong. Go to Settings-Information-SMS Center Number and check whether the SMS Center number is correct. You can change the number of SMS center (the number of local SMS center can be searched and queried online).
Specific operation steps (taking vivo Y79 as an example):
1, standby desktop click setting
2. Information
3. SMS center number
4. Change the number of the SMS center
Third, the mobile phone settings are abnormal, and the mobile phone will be restored to all settings. Go to Phone Settings-More Settings-Restore Factory Settings, and select Restore All Settings (without deleting any data of the phone).
Specific operation steps:
1, standby desktop click setting
2, more settings
3. Restore factory settings
4. Select to restore all settings.