Kia Optima-AC turning on in Off position

My 2008 Kia Optima is currently at dealer for the AC and they can't seem to figure it out...very frustrating cuz my warranty is up in 40 miles :/ 2nd time at dealer for this.
While the air is on, at a stop light or while driving, the air fluctuates - from heavy to light air flow coming out. 2 times this week, the air came on while it was in the off position. I feel it has something to do with the control panel, but who knows. The first time they had me replace cabin filter...no difference.
Today dealer says no issue, freon is good - cooling properly. I know that, that's not why I brought it in. I told them to keep looking, cuz I know there is a problem.
Any experiences with this, let me know, so I can pass on to them :_
Thanks!