This is NOT Okay
As leaders, we need to solve problems, including last-minute staffing shortages.
However, your team does not HAVE to work when they are not SCHEDULED to work! If you have potential staffing shortages, consider a voluntary “on-call as a backup” option for specific days or weeks, and COMPENSATE people who volunteer.
Some people WANT to pick up some extra shifts for financial reasons.
Others want or need to spend time with family or friends and are NOT available.
Your people are allowed to climb mountains with poor cell service on their days off. They are allowed to go out in a boat and leave that work phone on shore. They are allowed to travel out-of-state or have a couple of beers in their free time. Be the kind of boss who gives people the respect and compensation they deserve when they are on-the-clock, and respects their time when they are off-the-clock.
(image source: https://www.facebook.com/photo/?fbid=963287582468618&set=a.547025220761525)