If you use an iPhone 6 or iPhone 6 Plus and you updated your device to OS 8.0.1, you may have noticed a loss of cellular service and use of Touch ID? There is a fix available from Apple, and they recommend you update as soon as possible. This update also includes the updates and bug-fixes originally in iOS 8.0.01.
You can get the update here: https://support.apple.com/en-us/HT201394