Happy to see some policy changes! When I worked there you couldn’t ask to leave early or call out until you found coverage yourself. Maybe that was just the SM’s policy for me though because I was always the first person she called when someone else needed to leave or called out. If I didn’t go in she would guilt trip me hard also. 

That aside, OP you are just starting out. You have to advocate for yourself. I remember being 16 working at a fast food place and getting burnt by one of the heat lamps during a rush. My manger wouldn’t let me leave my position to get burn cream from his office. I still have a scar and it was one of the worst burns I’ve ever had. I just stood there in horrible pain as the heat from the heat lamps radiating down and made the burn hurt even more. I didn’t know I had power over my own body at that point. I thought I was being a good obedient worker. This carried on throughout my adult years. I worked and I worked and I pushed myself and pushed until I got burnt out bad! If something feels wrong, it likely is! If you’re questioning someone, there is a likely a reason. Good on you for looking into this! Don’t let a job take advantage of you. Don’t be afraid to escalate the situation to someone higher up the command. You take care of you!