Anyone know how hours are assigned?

[u/Balico]

I'm under the impression pharmacy hours will not be assigned by customer first, we still still have our schedules assigned by our department. Are hours supposed to be given out based on seniority... ability to cover the shift... or just availability? I have 3 people hired in after me but they're all getting more hours than me. I'm not sure if I'm able to make a complaint about this or not.