i work in the pharmacy and we are non-union, unlike the rest of the store associates. i convinced my manager to approve my availability request for saturdays. instead of 9 to 7 i am available from 12 to 7. i could go into why i am not available the first three hours of the day but don't think it's relevant. traditionally three or four people have worked the whole ten hour shift; we would rotate weekends and work every other weekend. for the past few months i've managed to split shifts with co-workers and also agreed to split others' shifts for them. i told my team that every saturday is not a problem so long as i can work afternoon only. there is one chick who for some reason is never scheduled on the weekends. i was told that we're not gonna be allowed to split shifts anymore soon.

i've recently been scheduled the 9 to 7 shift anyway due to supposed lack of staff.

if i should decide to put my foot down and say, no, i will not come in that day until 12, is there anything that can be done against me? i don't think the weekend rotation has been drawn fairly since that one chick doesn't have to work, but also there is another employee whose availability was just approved so she can work 9 to 4. i realize i could make my department mad and cause problems that way, but can i be written up or fired for refusing to work after being scheduled outside of my computer-generated availability?