Gino is right, the refs are only human, and referees or umpires
will miss some calls. Baseball umpires don't have the advantage
of video replays except on home run calls, and they get most of
the calls right. (except on balls and strikes.)
And as far as over or under serves, if your not sitting up front, you cannot tell from 30 or so rows back if it was over or under. We all had bad calls at one time or another. Some for the good ,and some for the bad. So, just be happy there is a game bad calls or not.