what would you do in this situation (work schedule related)?

This is perfectly understandable, you discussed your terms at the start of your employment, you're busy and you cannot change that! If you're on shift before Christmas Eve, I would mention it to another management member and just notify them that you had that discussion and you are still unable to work those days.

If you're not on shift, or don't manage to speak to another management member before Christmas Eve. Just continue without working that shift and don't worry. It is not your fault, and you are not to blame for any scheduling difficulties.

This Site Might Help You.

RE:

what would you do in this situation (work schedule related)?

BACKGROUND: So I work at a grocery store when i was hired i made it very clear telling all 4 managers and the supervisor that makes the schedule that i can't work on Mondays or Wednesdays. They messed up my schedule many times then a few weeks straight it was fine.

ISSUE: But now they have me...

One employer does not need to change the schedule for another employer.

If you want to keep this job, you probably need to make your schedule available on Mon & Wed.

If you don't care and just deal with the flack when it happens, do nothing.

I would work as scheduled or expect to be fired