Why Is this Guy in my group being so disrespectful?

He is in my discussion group. We get along quite okay during discussions. Everyone likes me. But, if ever this guy has to call me n I had changed my number, I let him noe. He says he will call (for discussion) but never does. I hate it because I am used to being respected by my group members. What is he thinking? Forgetful? Or, plain audacious?