If you’re asked to come in on a day off because another employee called out, that should count as overtime. Pay and a half at least.

The manager is literally asking you to give up your free time for their benefit. It should benefit you more than showing up for shifts that are your responsibility, regardless of hours worked. Employees being out is the managers problem, they can pick up the slack or incentivize people to help them when they have no obligation to. EDIT: Assume it’s a inconsistently scheduled, non full time job, like most food service jobs are anymore.