Well first of all, I wouldn't purchase the game 3 times if I was cheating, so for me it seems that something on my PC is triggering the alarm at Activision/Infinity Ward, but can't get an answer what it is, I formatted my PC before activate my 3rd game, created a new steam account, I NEVER play private matches except with my clan.
So my conclusion is that even if I have purchased 3 time, they still don't care, and that's what I call poor customer service.