Iphone app that allows me to send and receive texts?

I recently want to switch over to apple and decided to get an iphone. I'm paying $20 a month for messaging alone and I'm going to have to pay another $15 a month for the required data service. I want to only pay for one and was wondering if there's a text messaging app out there that allows me to send AND RECEIVE TEXTS WITHOUT MY FRIENDS HAVING TO GET THE APP? Thanks!

P.S. I use AT&T as a carrier if you need that!

Use an app called textme it's very good and also it's completely free!
But, the only thing is that you can't call.

Text free is your answer.