We currently have a Verizon Family Plan with two phones on it (no data plans for either phone). Is it possible to add an Iphone as an additional line on this Family Plan? If this is possible, what would the cost be for the monthly voice portion? I know you'd have to add the $29.99 data plan for the Iphone, just wondering if there's a way to add one without having to buy a individual plan apart from my current plan