Changeup!

[Baseballpitcher]

I think I've tried every possible grip with the changeup and I still can't seem to get a good sink or away action on it. The most recent one i've tried is having a circle change grip over the seams of a four seam fastball. I then roll my fingers up not even touching the ball really and cock my wrist back, it still doesn't want to move!? Any help is appreciated.