Settings that have been screwed up as a result of a bad update might cause your device to perform strangely, and the warning you're seeing could be one of the signs. In this instance, try to restore the original or default settings on your iPhone 7 by resetting all settings. Here's how you do it:

1. Go to the General tab in the Settings menu.
2. Reset may be found by scrolling down and tapping it.
3. If asked, enter your device's passcode.
4. Choose Reset all settings from the drop-down menu.