The number is identified as ppusa.  When I answered, they said something unintelligible.  When I said, "what?" They hung up.  A few hours later, they call again, I said hello 3 times and then heard a voice & they hung up again.

Started receiving these calls end of May 2015.  They don't speak, but call several times a day; some sort of bot/ robocallilng checking for active numbers is my guess.

Why do you bother to answer?

Rang my cell yesterday afternoon. Didn't answer as I know no one in this area code (Philadelphia), they left no voice mail. Likely a scammer.

They just called my home and told me it was about a refund for our electric bill. When I questioned what refund she said that is what she wanted to talk about. I told her I couldn't talk right now and she hung up.