Contact VZW (or Apple if you are eligible for phone support...if not you can visit an Apple store for help if one is available to you) and have tech support trouble shoot. You might also find some info on the Apple website forums. www.apple.com/support
You didn't give any details as to what happened during the update, did you keep the phone plugged in and running during the entire update process? Did you do anything on the computer during the update that could cause iTunes to hang?
If the iPhone does not fully complete a firmware update, it is possible that the update can "brick" the iPhone, in other words if you don't completely finish the update, it is possible to damage your iPhone
By the sounds of it, something happened that made the iPhone lose connection from iTunes (either the USB cable was unplugged, iTunes froze/hung or your iPhone froze/hung) because of this, your iPhone didn't fully update like it was supposed to and was bricked, the only thing you can do is take it into Verizon and have it replaced