It really depends on the place. I've never encountered one where the manager had total control over who was working when. Availability would be requested before

It really depends on the place. I've never encountered one where the manager had total control over who was working when. Availability would be requested before creating the schedule and one would be made up based on that. Even then, if you found you were scheduled for shifts you couldn't work you could request a change. Good managers would arrange it themselves, otherwise you'd have to organise a swap. That's not to say they don't exist. Some managers will certainly retaliate against employees who don't conform.