My question involves labor and employment law for the state of: California.

I work as a Senior art position with 15+ years of experience. My company is going to hold an event, for which they don't want to hire staff. They have requested every employee of the company to do an 8 hour shift to fill in all the positions they need to staff the event.
I was assigned to work at the event store, even though I have no experience in sales, no human relation skills. I am a professional artist. I requested to be exempted, explaining that I would do a poor job at this, and that this was completely outside of my job description. The request was rejected, as they only accept vacation and medical reasons.
What can I do?

Thank you