In my defense, I've had a phone hang up or do weird stuff because it couldn't tell the difference between a fingertip and an earlobe way too many times. Like, a shitty phone has nearly altered the course of my life because of this, and that's not okay.
You should be able to hit the power button while on a call and turn off the display, then put it to your ear. Much less effort than the people around you have to make to keep from slapping you
It's not just shitty phones, nice phones have this problem too.
I cannot for the life of me find the earpiece on new phones, my face dials and hangs up and does all kinds of weird shit if I try to have a conversation on the phone the way you're supposed to.