Tracer

I honestly don't know because I've never just flat out called off at this job.

Check your contract. Or ask your HR dept.

TraceOfSpades said:

Have you ever had a supervisor tell you that you can't request time off and you have to instead find someone to switch shifts with you?

What did you do?

Yes, it happens quite often. Sometimes the man-power isn't available for people to simply not be present, so switching shifts is the ideal choice. As for what you should, the answer is do what you're told.