Twice along the way I was approached with the "take this beeper, you're on call" thing.
I asked how they could possibly afford my overtime each time. I got a "you're not getting paid" line. To that, I replied, "Then expect my performance to be as such."
In the first instance, I was never on call very often. Mostly because I didn't answer the calls.
In the second instance, they got an answering machine.