phone plan? My friend is going to give me her old iphone 3g, so I won't be upgrading the contract. I am a part of my parents plan and in order for me to get an Iphone, I have to pay for the data plan (The one I'm doing is 25 dollars a month). If I pay for the data, will that give internet to my parents phones as well? Or just my iphone? will there be any extra cost or should this work out just fine?