I have a Sony Xperia with Android 8.0.0 Oreo.
When I speak on the phone, I first turn off the screen with the side button, then put the phone on my ear.
When the phone is on my ear, the screen often turn on and my fingers or my cheek or whatever touch the screen and do not-so-funny things.
How can I force the screen to remain off, or the touch-screen off until I use the side button again to turn it on?
edit: no "double tap to wake" option on this phone