Many users have been complaining a serious problem related to High Cellular Data Usage on their iPhone 6 and iPhone 6 plus. I am not sure 100% iOS 8 is exact the cause because this happens on iPhone 4, 5 after upgrading to iOS 8. However, we actually can fix this problem by some following tips.
Whatever the reason is, it would be nightmare because of very High cost of Cellular Data. Logically, we can fix the issue by finding and turning off completely all Use Cellular Data options available in iOS.
- Settings > iCloud > Documents & Data, turn off ‘Use Cellular Data’ and any other apps you don’t want to use data.
- Settings > iTunes & App Store, turn off Use Cellular Data
After all above, if you still encounter High Cellular Data Usage, you need to reset your iPhone 6 and setup a new iPhone: Settings>General>Reset> Reset all Content and Settings.