I want to get an Iphone 3GS. I have att already, and I'm in a family plan with my family. My whole family has unlimited texting already. I know the Iphone cost 30 bucks a month for the internet. So my question is: if I buy a 16GB Iphone 3GS for $200, will the only additional fee I'll have to pay a month be the $30 for Internet? (ignore the text and talk cost, my parents pay for that)