What criminal act happened to me?

hears what happened:I was walking home at around 12:30 a.m. going through a small park.I accidentally bumped into a lad with his other two lad friends. He then told me what are you looking at foo? Then I told them look guys I don't want any trouble and have a good night I turned around and walked away and it seen that they were going to let me go then I see I made a terrible mistake my cell phone buzzed I took it out of my pocket to see who was calling.The taunting grew violent suddenly I felt a blow to my head one of them kicked me there I fell over to the concrete and they began kicking me as I lay there.I struggled to get up but got kicked in the head again,luckily a police siren was heard the lads demanded my money stole my cell phone and fled away(one of them saying as they ran away so long sucker later days triangle face). Two witnesses who were my friends high school seniors came up to me and asked if I was ok and it was them who made the siren to scare off the guys.