If you are having a problem with your cellular data collection, mms, or Wi-Fi resetting the network setting might solve the problem.

This video will show you how to reset the network settings on your iPhone.

Steps
To reset your network settings:

1. Tap Settings
2. Tap General
3. Tap Reset (scroll to bottom of the screen)
4. Tap Reset Network Settings
5. Enter your pass code, if required
6. Tap Reset Network Settings to confirm (This will delete all network settings, returning them to factory defaults.)

Once your iPhone restarts, check to see if the reset fixed your problem. you may need to re-enter your wireless passwords if they were not stored in your iCloud keychain.