Unless you are on an old calling plan, you should be able to just add a data package (i,.e., $30 for 2 GB) to your line when you get your smartphone.
I did this last month, got 1 smart phone for the 5 lines I have with Verizon, and I lost the 700 shared minutes between all the phones. I THOUGHT I would only need to add a $30.00/month data package to my original plan, but it appears I lost the old plan completely, now I'm stuck for another 2 years.
I recommend that you Don't Do it under Verizon Wireless. Try and transfer your number to another carrier and use their smart phone. IF you plan on converting ALL your line to smart phone, then perhaps the new Verizon system will work - you do the math, but upgrading only one line is gonna cost you big time.
BTW, this is twice in 6 months that I've let myself get bitten in the butt by Verizon Wireless billing rules. The first time was their error, but their response was that I should have completely read the contract they print on those long register receipts in their busy stores before signing. I guess we're back to the customer is the quality control to ensure the work of their sales staff.
I thought the same thing, but must have missed something when I added the phone, because I got the additional $30.00/month but lost EVERYTHING in the old, so now I'm getting voice minute overages the past two months! If it was in the fine print somewhere I missed it.