I'm on the goddamned phone!

When I walk into someone's office at work and see that they're on the phone, I usually turn around and leave. When people walk up to my desk and see that I'm on the phone, they look right at me and start talking anyway. Consequently, I have the phone person talking to me, usually about something of moderate importance, and I have the real live person also talking to me at the same time. In the process of trying to listen to both of them, I usually don't hear either of them. I then start ignoring the real live person (who shouldn't be talking anyway&#41 and, sounding like a total incompetent boob, have to ask the phone person to practically start their conversation all over again. The alternate version of this is when someone "voices in" to your phone extension and repeats your name over and over and over again, maybe hoping that they will eventually annoy you into answering them. I've actually had someone do this to me and when I didn't answer (because I was on the phone, not because I was pretending to be away from my desk, as I am sometimes tempted to do&#41 the person actually walked over, stood a few yards behind me and literally yelled my name a couple of times. Can't people just wait two minutes or put a note in front of me or something?