How to Hard Reset iPhone 7 or iPhone 7 Plus.
Step 1: Press and hold the Lock/Wake button on the right side of your iPhone.
Step 2: At the same time, press and hold down the Volume Down button on the left side while keeping the Lock/Wake button pressed.
Step 3: Keep holding both the buttons until the screen turns black and then switches back on to display the Apple Logo.
That's It You Done.