Unwanted outgoing calls, "butt dial"

Do this:

Open Settings

Tap Accessibility

Tap Touch

Turn off Tap or Swipe to Wake

Now your phone will no longer respond to touches when in your pocket. BUT, you will need to tap the side power button to wake your phone going forward.

Lock your phone with the side button before putting it in your pocket.

That's a good question. But then we don't know if the Author uses FaceID or a passcode on their iPhone? That said, I can't count how many times, people have come here because they do use a Passcode and have locked themselves out of their iPhone from unintended taps on their screen while carrying their phone in their pocket.

I truly believe the best way to protect against unintended touch is to turn off tap or swipe to wake.

The phone will still wake with Tap or Swipe to wake enabled. What I suggested is really the only way to stop it, if someone carries their phone in their pocket.

How would it bypass Face ID to make the call? When I lock the phone, it may wake, but will not move past the Lock Screen.