The neck should just snap off.
What Ive had to do before on some hard to open ones
(ones that would break in my hand) is hold them realy tight
in a rag or towel (whatever) Leaving only the necj exposed then give it a good tap with the but end of a butterKinfe. Not the cleanest break
But it works.
Kawasaki had the best advise for the hard to open ampules.