How do I stop controlling parents from getting mad at me?

Alright, so I'm in college and have been on my own for a while. I come back home from summer break and I need to get this sheet signed by an advisor. I listen to my parents and they say to call the department. So I do, and no answer. I wait and then try again, and no answer. Then I tell them and I am told to call my Air Force ROTC Detatchment, but I tell them that it would be useless because he said that I need my doent signed by an advisor. So they say to me 'why are you so scared of calling your Det' and I say 'Because I'm not supposed to go straight to the Det with a question' and they say that I should just try and I say 'everything is always so stressful'. So they flip out and yell at me and tell me to do whatever I want and go and slam the door to their bedroom. This has happened more then once and I'm not sure where to go from here.