How are texts, calls, 911 calls prioritized?

I think this could be helpful for those thinking of moving to pre-paid so I’m asking.

If someone with Mint(for example) is trying to make a call or text at a concert is it possible they may not go through? Would a 911 call go through?

In my mind texts and calls should always go through as they use so little data compared to TikTok, YouTube, etc but what do I know.