My boss called me the other day asking me to come in on my day off. I refused as I had something to do. He got pissed at me and now I'm hearing talk of being fired for it.

I have been at the place for 4 years, never so much as gotten a warning. Always on time and will usually cover if need be. This was the one time I didn't want to come in because of something was planned.

Yes, I do work in a right to work state.

Is there any legal recourse or anything I can do?

Edit; holy Jesus guys too many replies to read lol I will try to read them all. Thank you all

Edit 2: sorry I confused right to work for at will employee. My fault