Job laws for minors Wisconsin?

I work at Mcdonalds's im a minor and they hold me way after my shift is over like 30 mins they wont let me call in when I'm sick they say that its not there problem and hang up and I'm expected to be there. They always throw me on grill and one time I burned my arm bad enough where the skin was bubbling and they didn't care to put burn relief or anything like that, I asked to switch positions and they wouldn't cause hot grill next to a burn hurts.