The default pawn has a floating movement component and processes input *automagically *(not only WASD but Q, E Space and Arrow Keys, too!). But you can override it via input consumption. Where are you handling the input?
If I do this in the Level Blueprint - which has higher input priority - and A here is set to consume input:
The default Pawn no longer moves when you press A.
I did not add / spawn a pawn. It’s in the blank template.