This Boy wants my number :\?

There's this dude that I don't even know.(He has a Girlfriend and I have a Boyfriend) He just graduated highschool and I'm a freshman. And he messaged me over facebook and wants to text me. I'm not attracted to this guy, and I don't even know him at all. But I don't want to be mean and tell him not to text me :\ but it looks like I'm gonna have to...what should I do?! :\