The biggest thing is finding someone, whether it be you or someone else, that has unlimited text and voice as their plan.
Then, I'd have him go set up a google voice account
that will be attached to a current or new gmail account he creates. Just go through the step by step setup process and at some point it will ask you to choose a phone number, and attach that number to an existing number for verification. That number will be the one with unlimited plan. Google will call the existing phone and give you a code to type in to finalize creation of the new number.
Download google voice to the rooted phone, and also download Groove IP Lite, (or pay the 3.99 or whatever for the full version, I did). Those two apps will now serve as the new Telephone app (GrooveIP) and Messaging App (Google Voice).
There are a couple settings you have to change online too. In the upper right hand corner of the main google voice sign in page there is a little gear that brings up the settings menu. Make sure the checkbox for "forward calls to" is set to "google chat" and NOT the number of the unlimited phone that this account is attached to.
After that's all done make a few test calls between the two. The phone that the new account is attached to will never be able to call the google voice number, but the google voice number CAN call the unlimited number to which it's attached. The unlimited number CAN text the google voice number though.
Groove IP also has some settings that can be changed on the phone. Dependent upon the phone you may need to tinker with those options a bit to minimize delay (inevitable to a point) and maybe make the sound better. Beyond that, once it's setup it's good to go.
you're not the girl you think you are