The number called, I answered and no one was there. I kept on the line listening, and it was silent, but still an open line. The caller didn't hang up for about 2 minutes. This is a tactic used by skip tracers - which are hired by debt collection companies to find people the debt collectors can't find. When you get a call like this, where the caller is silent but not hanging up it is because the caller is listening to background noise to see if they can hear someone, possibly the person they are looking for. If you get a call like this, stay on the line, say nothing, and wait for them to hang up. They'll eventually stop calling after about two weeks.