A. Meet with the person who is applying the unwanted pressure (it works best one-on-one, so if more than one person is pressuring, you may need to figure out who is best to speak to).
B. Frame your concern as asking for advice. For example, "I'm struggling with how to handle this on-call thing. Work-life balance is EXTREMELY important to me, but I love my job, and I don't know how to set that boundary without upsetting management. What would you do?"
In my experience, this approach makes the listener very sympathetic and pragmatic, and they advise you to do what you already want to do (and subsequently stop pressuring you to change). I think this is because people like being asked for this sort of help, and when they enter "advice mode" they take a step back and look at the situation from an impartial distance.
YMMV, IANAL, etc., but it's served this awkward introvert quite well.