why don't friends call back?

I have a friend that I'm really worried about. I have left multiple messages with no return call. The one time I've seen her since March has been when I stopped un-announced at her home.

Note to all my friends: Call me back! If you don't like me and don't want to be my friend, tell me!

I don't take hints very well. I'm going to keep leaving messages. Next step is writing notes. Next step is another surprise visit to make sure you're still alive.