How can I stop my iPhone from unlocking in my pocket?

I often use my AirPods or other headsets during the day to stay as handsfree as possible. Whenever I make or receive calls, then lock my phone and put it in my pocket, it then almost without fail unlocks while in my pocket. The annoying part is that it then either randomly disconnects the call or some buttons get pressed while I'm still on the call and moving around.

Even if I press the power button, through my trousers, to lock the phone again, it automatically unlocks again.

Is there a foolproof way to ensure the phone does not unlock?

[Re-Titled by Moderator]