Don't pick up already
Okay, people, let's talk here. Or not talk, which is the point I'm about to make.
If you can't talk to me on the telephone when I call, DO NOT ANSWER THE PHONE. I'm calling to talk to you, that's why I picked up my phone, dialed your number, and sat through the ringing of the phone, waiting for you to pick up. If you pick up, that indicates to me that you're ready to talk.
If you're not ready or available to talk to me, don't pick up the phone. You have voice mail. Guess what? I can leave a message on your voice mail for you to pick up at your leisure.
I know, I know. This seems to be a foreign concept to many of you - let a phone ring? Without picking it up?
Sure!
Why not?
I do it.
If I'm talking to someone, on the phone, via IM or in person (shock, I know!), then at that moment, your call doesn't rate unless I'm expecting your call. If I'm EXPECTING your call, I'll let everyone else know that none of them rate over you before I answer that phone. However, if I'm not expecting your call, you can leave a voice mail. I'll listen to it. Really. I promise. Eventually.
So, let my call ring. DON'T ANSWER THE PHONE. I'll leave a message, and you can call me back.
Trust me, it's less offensive than your "Hello? Hi. I can't talk. I'll call you back later." answer. Can't talk? Don't pick up.
Sheesh.