I had that happen with balloon head 45LC cases. Luckily I was using a very old RCBS die, one that had a huge opening for the decapping spindle. Do this off your press, preferably in a vise, so you don't damage your press. I recommend brass punches not steel. I was able, from the top, to get some of the case mouth to bend in. And then worked my way around the case mouth, knocking the case mouth down a bit at a time. Once I had a firm "ledge", and a drop of oil about the inside, I used a larger punch. That removed the case. Expect to spend about a half an hour doing this, be patient, and don't grab for a bigger hammer. If things don't work out, go away, mow the lawn, etc, and a better solution will come to you.
I recommend for the future, lube your cases. Yes, yes, that is why you purchased a carbide case, so you don't have to lube. But if your cases are that deteriorated, or so ballooned that they pull apart in the sizing die, lube them. Notice how effortlessly lubed cases are in a carbide sizing die, the difference in sizing effort is surprising.