Why are switches grayed out in the iPhones Settings app with iOS 8.3? In 'Settings' > 'Cellular': all the switches under 'Use cellular data for:' are grayed out. Some are ON and some are OFF but none can be changed. These are the switches that control cellular data usage for individual apps. Why are they disabled?

In the same panel I have 'Cellular Data' turned ON and "Enable LTE" turned ON.
Looks like it's restricted —someone activated parental controls on your device.



Go to Settings > General > Restrictions and scroll down until you see the Cellular data item, you can deactivate it there (given you know the passcode).

On iOS 13, restrictions have been moved under Settings > Screen Time > Content &amp; Privacy Restrictions