If your touch-screen is unresponsive or you can't quit a troublesome app, then reset your iPhone. Press and hold the “Sleep/Wake” button and “Home” button at the same time. Don't release either button until you see the Apple logo appear on your screen about 10 seconds later, indicating a restart.
Simply so, how can I force my iPhone to turn off?
Reset your phone if the device does not respond to a power-off procedure. Hold down the "On/Off" button and the home button on your iPhone at the same time. Continue to hold down both buttons until the Apple logo appears on your phone and it reboots.
Why does my phone not turn off?
If your iPhone won't turn off try forcing it off by holding both the sleep/wake button and the home key for about five seconds. Continue to hold until the Apple logo appears. Your phone should now power on and off normally.
How do you turn off an iPhone 7 when the screen is frozen?
Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the Apple logo. On an iPhone 7 or iPhone 7 Plus: Press and hold both the Side and Volume Down buttons for at least 10 seconds, until you see the Apple logo.