Replying to Your rights with police...

Long story short, just had a nice run in with the police...im not even sure if they are police. its the police run by my university, anyway. did everything they asked answered there questions, but being only a 20 year old i was scared it was my first run in with them and i didn't do anything apparently there was a mix up in my apartment and they thought our room had people in it who weren't signed in. So after answering the questions i pulled out my phone told the office i was calling my mom, showed him the screen so i could make sure i was in the clear, didn't even hold the phone to my ear held it sideways so he could always see it, and after about 2 rings, it was now apparent that i guess i wasn't allowed to make a call, the police then decided the only way this scared 20 year old kid was gonna hang up a phone call with his roommate was by pinning him against a wall, grabbing his wrist, and taking his phone. Now I'm not a police guy, i know maybe more then the normal person about my rights, but can someone enlighten me with these laws along these lines. Are you allowed to make a phone call while answering/answered the cops questions, mind you i told him and showed him. and is he allowed to touch(push, grab, and push) me for doing so. Like he never said no till like 3 rings it didn't make sense, he could have just been like no phone calls or can you hang up, not just go full linebacker stance and grab my wrist and phone, I'm a scared little college boy who's 20 and was playing freaking COD all night.