Can an employer make you on-call while working your shift. Make you work while on-call. To try to keep the building covered. I know it's confussing that's why I need help.

How can you be "on-call" if you're already there working? :confused:

We are at work and they tell us that we are to stay at work if someone call in. Then they call that 'on-call'. So if someonne call in, they tell us that we have to work there shift or be fired.

Ok, then YOU aren't on call. You are required to stay in case somebody else does not report to work. Generally speaking, that is "engaged to be waiting" and is compensable.
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_785/29CFR785.15.htm

You can file a claim for unpaid wages with your state Dept. of Labor.