What should I do if the iPhone 6 phone is connected to the 3g number and the SMS keeps showing that it has not been delivered?

If the mobile phone can't send short messages, you can try to restart or change the mobile phone for testing to see if the following conditions exist: 1. The SMS center number is set incorrectly; 2. No signal or low battery; 3. Because the system is busy during the holiday short message sending peak period, it is suggested to try again later or avoid the sending peak period; 4. The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number; 5. The short message sending time exceeds 24 hours; 6. The mobile phone shields the short message sending function; 7. Blacklisted by SMS; 8. Insufficient quantity balance; 9. SMS inbox and outbox are full. 10. If you want to check whether the SMS function is turned on, you can contact the local manual customer service. If the above reasons cannot be solved, it is recommended that you contact Unicom's manual customer service for consultation. 4G national unified tariff, no matter where you go! Click /sAbMO for details. The flow is not cleared across months and is valid for half a year. Click /sAAGL to enjoy a 20% discount!