What phones are available with this offer?

I am really interested in an offer that I recently heard about. A friend said that she had seen some sort of mobile phone offer on the internet that gives you a free line rental. I am wondering which phones are available with this 12 month free line mobile phone offer. Does anyone know where I can find more information about this great deal? I need a new mobile phone, and I have been paying way too much for the phone line so it would be nice to have a free line for a while if it is possible to get it.