Iphone problems
My iPhone will not let me open iMessage or open iMessage settings? what do i do? i tried restarting my phone and it did not work.
iPhone 5s, iOS 8.1.3
Did you try to reset the phone by holding the sleep and home button for about 10sec,until the Appel logo comes back again? You will not lose data by resetting, but it can cure some glitches.
Any restrictions set up in Settings/General/Restrictions?
If this does not help, set it up as new device, as explained in this article:
How to erase your iOS device and then set it up as a new device or restore it from backups