So whats the real monthly cost to add a dummy line to AT&T so I can get another 5s at a subsidized price. I read that you add a line, pick a data plan, get the phone $199 (16GB) and are then able to transfer the phone to one of your existing numbers and then cancel the data plan on new phone? Then I read the monthly cost is just $10 (24 months), and other places I read the monthly cost is as high as $30. Can someone please explain this for me? EDIT: I am on a "Family Talk Nation 550 with Rollover" plan with $30 Family texting. And I'm asking here and not at the AT&T store because honestly I believe "most" of the folks on here know more then the typical AT&T CS. Thanks.