@chill_ice, I am saddened why this has happened. Personally, this would really frustrate me, however, understanding that everything happens for a reason would make us look back and ask why this happened, I am sure God has better things for you.
If this happened to me, I will surely ask DIAC/CO with regard to their decision. I strongly agree that this should have been an inconsistency with your course. By the way, what happened when you got your interview? Any specific question related to the course that you were taking up?
Same as everybody else, I would look for a way to appeal to their decision.