okay say it is sunday, FIRST DAY OF THE NEW PAYPERIOD, and you get called into work and it will be overtime so you do it. the next day you are told that they redid the schedule and you would lose the overtime that you had already worked. IS THIS LEGAL IN THE STATE OF IOWA?

If it's the first day of the new pay period, how can it be overtime? It's not overtime until you actually WORK 40 hours a week. If they call you in on a day you are not scheduled to work, and then send you home or tell you not to come in later in the week so that you do not exceed 40 hours in the week, that is legal in every state.

If it's the first day of the new pay period, how can it be overtime?

the schedule for that week was already out I was scheduled off the first sunday of the payperiod. I came to work. I already was scheduled 40 without working on sunday.On monday she called and changed the schedule. Does that still make it so?

Yes, it is. They are allowed to change the schedule so that you do not work over 40 hours in a week.

thanks but now I know not to work any anticipated overtime until its the last day of the week.

Just so long as you understand that barring a bona fide contract that says otherwise, you can be disciplined or fired for refusing overtime. Or for failing to work any hours the employer says to work.

We are not required to work overtime it is strictly a volunteer basis. But thanks I will keep that in mind as well.