Yes you should be able to keep it because you are not upgrading your line you are just switching devices out check with Vzw before switching first but you should be fine.
PLEASE NOTE I DO NOT WORK FOR VZW
Since you are not on the same account, you should also keep in mind that the warranty of the phone will become void and the insurance won't be available to you. You would be considered the second owner of the phone and those items don't transfer from the original owner (your parents) to the next owner.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
It would be better to add a line so you have warrenty as Ann said. With these phone there so costly that you might want to consider it. With the unlimited you have to pay full retail or add a line if you didn't have your parents to get you one.
I agree with Ann that the warranty with vzw may be voided but this is just with vzw you will still have the warranty with apple and as far as the insurance goes just get apple care for 100.00 if you do this this has nothing to do with vzw
I did talk to a manager at a verizon store yesterday. He said that if we were to "switch" phones and activate it on my line that I would be charge the difference in the subsidized rate. Basically he said he's tried this before and it doesn't work, but it also sounded like he was making it up as he was going along. When I called verizon, they said it would...? I'm getting conflicting answers...