I want to add a new line on my plan for my girlfriend, currently I have an individual plan with the unlimited data on my iphone 4. So I plan to switch to a family plan since its better discount, however I'm a bit confused. Currently I pay about 100 dollars per month. If I add another line will I still be able to keep the unlimited data plan? Also will I be paying like 200 dollars per month? Since now there's two phones?