What to do if the mmI code is always invalid when setting text messages?

" It is recommended to operate as follows:

1. Restart the phone to see if it is a signal problem.

2. Settings-Application Manager- Sliding screen options (all) - find information - click to enter, clear data and try again

3. Try changing other SIM cards

4. Check whether the security guard or the third SIM card is installed on the phone. Third-party SMS software, uninstall and test

5. Back up mobile phone data (phone book, text messages, multimedia files, etc.) and restore factory settings

If the above method still does not work, please Send the machine to the service center, and the engineer will inspect the machine and handle it"