I get laid off every summer for 4 months

I maybe work max 4 or 5 shifts a summer. So i decided im going to sublet an apartment for the summer in the city so i can actually enjoy myself and not sit around in a dead small town doing nothing. I told work that i can still make the trip back home (2 hour drive) for the very few shifts i have but to feel free to schedule away my shifts to people with more seniority than me or to whoever wants them. This bitches ofc had to have a problem with this. "You can't just leave, you're still on the schedule" yes i know, which is why i said i will work my scheduled shifts. "What if we need you?" If I'm not scheduled and you call me asking if i can work I am ALLOWED to say no. You can't FORCE me to work like you think you can. You can't legally say "No actually you have to come in" (they've done this to other people before) Now my union rep, head boss, and boss want to speak to me in their office thursday morning.... All over the fact im moving 2 towns over and said i can still work those maybe FOUR shifts i will have this summer. Like..... anything to make drama. I am not sitting around all summer AGAIN waiting for the odd chance i get a shift because YOU laid me off!!! I am going away for four months. GOOD BYE. It is not more complicated than that.