Hello, so I just purchased a blackberry 9530 for my gf and wanna get her a plan - however her sister is paying her bill for her current verizon phone. I guess the sister has her and her younger brother on a plan, possibly a family plan. The sister has a smart phone from what I remember, so can I add this phone to the current plan? Also - my gf and her brother only have minutes, which they all share... the sister has a data plan... If I could add this to their current plan, how much will I have to pay? I wanna get her the least cost plan that I have to for this phone. I'll pay it for a year then let her pay the rest 
Thanks in advance.
Thanks in advance.