How to find out someone's text messages for free?

Is there an app or website I can get to read someone's text messages? I have an iPhone and so does the other person-dont ask about the relationship between the two of us, it doesn't matter, but can someone suggest a free way to read someone's texts? I can get the persons phone to read the messages so I need another way, I don't need to know who they call, just texts thank you for all advice!

I think pinger is one, if not I'm sorry. :-/

What the hell is wrong with you? Don't you know that you're publicly asking people how to commit a crime?