Proximity Sensor - iPhone 7
How can I lock the dial pad during a phone call, so that I don't accidentally press a button during a call?
iPhone 7, iOS 13
Question marked as
That should happen automatically when you move your device to your ear thanks to the proximity sensor, unless it is broken or obstructed by a cover or screen protector that interfere with its activity (check that, and eventually remove case and/or screen protector).
If the issue persists, have your device inspected at an Apple Store or Authorized Service Provider.
Regards
Giulio