Ok, for those of you still having trouble with this, it's much easier than you think. As long as you have someone on your plan has an upgrade and doesn't have unlimited data (or doesn't mind giving it up) you can do this with ease.
So here's how it worked for me.
-My Dad had an upgrade on his line (He has a 4S with 2GB data)
-I simply ordered the phone using his upgrade (I went through Target, but should be the same process for everyone).
-When it arrived, I kept everything sealed.
-I went to Verizon.com and did the Switch/Activate device button under my Verizon.
-I then selected my line and said activate device.
-I was then prompted to enter the ESN/IMEI/MEID number. Just look at the back of your iPhone 5 box and enter the numbers.
-I was then prompted for my SIM number.
-Open the iPhone 5 box, take the phone out WITHOUT turning it on.
-Open the SIM slot with a paperclip or SIM ejector tool.
-Look at the numbers on top of the SIM card and then enter those numbers on Verizon's website.
-After continuing, it'll probably feed you BS saying your plan may not be compatible.
-When you get to the part where you select plans/data just make sure your unlimited data is selected (it should be by default).
-Once you've confirmed that it is, continue and you should be all set!
-You may have one more confirmation in there afterwards but it should just be confirming what you've already confirmed with them.
No need for SIM switching, calling Verizon, etc.!