Guy likes me but I don't like him?

There is this guy who goes to my school who likes me (he told me), but I don't like him back. I already kindly let him know that I don't see him that way but I'm not sure if he understands haha. First of all he texts me almost everyday, and I can deal with that, but then he starts asking me out and now instead of texting he calls me! I usually don't answer his calls just because I don't feel comfortable talking to him on the phone. What do I do? How can I let him know nicely that I don't like him and don't want to hang out with him?