T-mobile: Kids are free?

So, I saw a T-mobile commercial that says kids are free until 2012. And I thought to myself, "There must be a catch." I have a family plan, but one of my children doesn't have a phone and he really wants one. If I added my child to my family plan, does that mean I don't have to pay for his phone service monthly until 2012? Does it matter if I already have a contract with T-mobile?
 
Back
Top