Apple® iPhone® 7 / 7 Plus - Erase All Content and Settings
Erasing all content and settings may help with a blank or frozen screen, apps crashing or freezing, keypad/touchscreen problems, can't hear, device making noises, can't make or receive calls and device won't sync.
Erase all content and settings only if absolutely necessary as it removes all data including:
If you are signed in to your Apple ID on another device (known as a 'trusted' device), you may be required to enter a verification code sent to that trusted device upon reactivation.
An alternate method (restore via iTunes) is available if the device is unresponsive or won't power on.
For specific error messages related to iTunes update and restore, refer to iOS update and restore errors. Advanced iTunes troubleshooting and configuration should be handled by Apple (scroll down to "Product and Technical Support" section).
From the Home screen, navigate: Settings > General > Reset.
Tap Erase All Content and Settings.
If presented, enter your passcode.
Tap one of the following:
Backup Then Erase
If a backup to iCloud is currently in session, you screen displays 'Finish Uploading Then Erase.'
Allow several minutes for the reset and reboot processes to complete.
To set up the device after the reset has completed, refer to Initial Activation and Setup.