Somebody help me (being hacked)

I'm international student, so I came to America for studying abroad. There was 3 days ago, a strange number called me that their company was expired so it wanted to give me $200. The caller told me if I had a laptop with me. And I said yes. He told me to download Teamviewer. So I installed that program. After that, he could able to control my laptop. He brought me to westernunion.com for money transfer. Fortunately, I don't have any credit or debit card. I asked him if he could send me money by address, but he said he couldn't. I told him that i would ask my family when they were home, then i would call him back in evening. After that, i told the story to my family, and they said that caller was a liar. So, i dont call him back again. But today i turned on my laptop to watch some shows, but the Teamviewer just popped up and my mouse was controlled by someone. I was freak out and press the turn off button. Now I dont know what to do. Someone help me!