How can I communicate my needs to my boss in a client facing role where I can not leave my post without getting dismissed or ridiculed in front of customers?
Note: Although I no longer work at the job in question, I never learned how to deal with this. I would like to know how I and others in similar situations, like my sister working there now, can handle such a thing.
Background: I worked in a supermarket as a cashier. This is a huge international chain. Multiple situations happened where my colleagues and I got treated badly after requests to our boss. Boss here refers to the person that is in charge of my department and is my direct supervisor. All cashiers including me are between 16 and 20 years old, the boss is in her forties.
Example 1: I was running low on change. I asked my boss if I could have some more change when she walked by. She was constantly running around, so I could not phone her up. She told me no, she would not open the safe for just me. Half an hour later, I was completely out of change and was unable to pay out a customer exactly. Protocol says I have to round up their change at that point. My boss, walking by while I was doing that, asked what I was doing in a rude manner, since the customers had hands full of change (4 euro in 10 cent coins). When I told her I didn't have the proper change, she scoffed at me in front of the customers.
Example 2: It was extremely busy in the shop and we were understaffed. It was 30 degrees Celcius and I had been working for 5 hours straight without a break or even a drink (no drinks allowed on post, company protocol). Normally our boss tells us when we can have a break. When she walked by I asked for a break, but she told me I could not have one. Two hours later I still hadn't had a break, but bakery department's boss noticed. He sent me on a break.
Example 3: It was extremely busy in the shop again and we were again understaffed. I had been working from 8 till 2 without a break, so I asked the boss if I could have one after dealing with the customers who had queued up at my cash registry while I was asking. She disparagingly asked why I didn't ask one before, as I had messed up her break schedule, in front of the customers.