What do i do

If your preschooler is ignoring you then it sounds like he either has a hearingproblem, or there are not enough consequences for his ignoring you. When you say the word no, then try physically moving him away form what ever it is that you don't want him doing. Then implement a "sitting in the corner" conseqouence as he gets a little older, or figures out how to wait until the las minute before he gets up and moves himself. The key here is to have your consequence occur as soon as he doesn't comply.