Why hasn't my friend been calling me?

I called her two weeks ago and she never called me back! I understand she has her school and school assignments but I know she isn't THAT busy. She is only a part time student and she should make time to call. I called her again just now, no answer! Maybe I should just give up and maybe she don't wanna be my friend anymore. I'm fed up with people using "busy" as an excuse! My other friend hasn't been calling me back either. I called her two days ago. I know she has two children now and married but at least CALL ME!