You should be able to do this. You have two options:
1 - Pay retail for the new device and trade in old device, get 200.00 off retail (this option is available on the website, so no reason it shouldn't be in store as well).
2 - Do the upgrade route, but know that you will be required (last I read at least) to keep a data package on the line you upgraded with. So you'd need to (I believe) keep a 30.00 data package (or some sort of data plan) on the line you upgraded *WITH*, for the 2 years. It's Verizon's way of saying "We like to screw our customers".
There are other options (I think the Best Buy one may still work, but not sure - you'd have to search for it), but those two are the ones that I'm most familiar with.
Verizon will do all they can to get people off unlimited, including lie to them. Again, the option to purchase at full retail and still do a trade is offered on the website, and while I'm sure that's not the option you were seeking, it is one that's possible. If you do the upgrade route on the dumb phone line, you'll have to pay for data on that line for 2 years though.