What are you talking about? If you have registered online with reliance by giving your email id, they will send bills and emails there. If not, they will send it to your postal address (you get your monthly bills don't you?). Whenever you download something, you leave a trace, your ip being the first piece of information. Someone seems to have complained to reliance and provided them with your ip and a timestamp using which reliance has identified you.Tell them that you won't do it again. And go and read a guide on how to use torrents/ p2p safely, or better still, stop using it.