TS2755: iOS: Troubleshooting MessagesLearn about iOS: Troubleshooting Messages
Currently Being ModeratedJul 27, 2013 11:18 PM (in response to Franknap)
Double tap Home button, delete the app the do a reset.
Reset: Hold down the Sleep/Wake button and the Home button at the same time for at least ten seconds, until the Apple logo appears. Note: You will not lose any data
If no joy, contact the app developer.
Currently Being ModeratedJul 27, 2013 11:53 PM (in response to Franknap)
Since you've said SMS app, now we known it's Messages app since there's no stock SMS app (it did with the iPhone 3G).
BTW, SMS is a carrier service. Have you contacted them?
If you did try 1 step at a time
1. Try in Settings > iTunes & App Stores > Apple ID > Sign out and sign back in.
2. Did you tried Restore from backup using iTunes.
3. If no joy, restore as new