So originally I had a clean play shift today, from 8:30pm to 10:30pm. Cool. Earlier in the week, my SM asked if I could come in an hour early. No problem. I ended up making plans before my shift, and would go straight to work after. I woke up this morning from one of my shift managers saying that plans changed for today, telling me (not asking) that there is no clean play tonight and I will be working 1pm to 9pm instead. I let my SSV know that I had plans and I wont be able to come into work until my originally scheduled 7:30p to 10:30p. Is this even legal? Am I obligated to work a shift that has changed without my consent 6 hrs in advance?