Unsolicited calls several times weekly

We get several of these unsolicited calls weekly.  When we pick up, we hear either nothing, or a noisy background and no one responds to our "hello?"s.  Annoying.  They JUST CALLED RIGHT NOW, got a live person with a noisy background and told her what I'm up to.  She was stunned, asked if I get calls from them (no duh), and said goodbye.  Bet there's plenty more where she came from though.