She does not want me to as a friend, did I screw up?

To make a long story short, I really liked this girl(Who has a BF) at school (I don't see her anymore). I asked for her number and she gave it to me. I waited a couple of weeks to call because I didn't want to seem like I was smothering her; but no response. I tried again and no response. I found her on facebook a few months later and she denied me. I know she pretty much adds anyone she knows or has known on facebook. Did I screw up because I called her?