Oh, I know about those, quite annoying. I remember one day I was real pissed off at something (I don't remember what was teh reason, but I was just in a hell of mood anyways)
the phone rang and I picked it up, said "hello?" and no one answered..... I said "hello" again, several times, and it felt like if they were listening but didn't want to say anything... well, I just got so pissed and began cursing them in a way that if you heard me you would be like