too many would abuse it without mute button. I vote for calls if we also gets mute, vote against if we dont. If i get a call while busy with something else, id close the game, and continue what i was doing, then log back on when done. This is the internet, you are 100% certain to get troll calls MANY times.

edit:
if hes gone for 20 minutes, kick him and find someone else. too many will call random people for a laugh.