Question about upgrading/switching lines

My sister and I are on the same Verizon family plan with the rest of my family. Anyway, I can upgrade my phone now and she can't until August. I haven't gotten a new phone because I am waitin on the a990 to come out but she wants to get the Razr b/c her LGVX7000 is starting to crap out on her (like mine did). I have been using an older phone until I get a new one. I was wondering if it was possible to go and upgrade my phone but then go online and switch the phone to her name and then do the same when her time comes around. I have only switched to older phones and was wondering if the system would let me put a new phone on her line online? I don't want to go upgrade and try it and then be stuck with a razr I don't want. Thanks

if you are eligible for an upgrade, then use your upgrade to get your sister a new phone, then after that is all said and done, do what is called an ESN change back to her number. Then all you have to do is wait untill the phone you want comes out, then use your sister's upgrade to get your phone, then do the ESN change back to your number. It's kind of complicated, but a rep would know what you are talking about. You can print this off if you need it. GOOD LUCK!!