Credit to Johnny Sanchez post on IMore.com
"When you upgrade to iOS7, you have to reset your network settings and have iMessage and FaceTime off in order to correct the issue. The upgrade simply doesn't recognize your previous iMessage and FaceTime settings because these features are unique to the software.
Tap Reset Network Settings
Confirm the changes and re-add your wi-fi password(s). When the device resets, make sure you make sure after re-adding your passwords, the iMessage and FaceTime is activated by tapping them in the setting app. Make sure they're on.
You should be all set."
This works. Myself and a friend have followed instructions and it has fixed the issue.
If you have any other problems either drop a comment or fire off the links below.
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