The only way you can pull a shot is to make contact with the outside part of the ball. Sometimes this comes from swinging into impact from outside the target line, called "coming over the top," but other times the right wrist simply straightens too soon, which causes the toe of the club to rotate closed (above, left,). In both cases, you hit the outside of the ball--and yank it.
Get a feel for hitting the inside part of the ball by making practice swings with your right hand open on the grip. Focus on keeping the palm behind the shaft and pointing at the inside quadrant of the ball through impact (above, right). You'll keep the face square and start the ball on line.