Dunkin' Donuts review: Employee complaint

So I Work for Dunkin Donuts in Stratford Connecticut. It started off great! But lately it just has become a very stressful workplace. I am scheduled to work a certain time like from 5 am to 12 pm. I never get to leave at exactly 12 because the my coworker who is supposed to come and relieve me. But, they come 2 or 3 hours late. Or they don’t even come in. So I have to always stay extra hours to make up for my coworkers shift she was supposed to cover but I tell my manager and she doesn’t do anything about it. It’s the same every day with them. Nothing gets done about them and I am super tired of killing myself at work. I just can’t take the way me and one other person gets treated. Making us stay over our schedule. Plus, we don’t get any breaks we work 6 to 8 hrs straight with no break. Almost every time I come into work and I never get a minute to just breathe and take a drink. Half the time I’m dying of thirst. I’m just so tired of the mistreatment that happens .