Does anyone know of a free phone reverse lookup?

A number called me tonight and asked who I was, when I said that they called me and I wanted to know who they were they hung up. I called back like 10 minutes later and a man answered and got really pissed that I called and kept asking where I got the number and never to call again. I'm curious as to who it was, I don't want to pay to find out does anyone know a free reverse thing?