The simplest way to describe a Factory Reset using the options in settings is this:
Your data is wiped (your apps, your contacts, your files, your pictures, your music, etc.), but the actual operating system (Jelly Bean) remains exactly the same as the day you first downloaded the update package. What they are telling you to do will not fix your problem if you have already tried a factory reset that didn't work.
Think of it this way: If your Windows install becomes completely unusable or performs poorly no matter what you try, you have to reformat your hard drive, install an entirely new copy of Windows, and then replace all of your missing data and applications to fix it. That is a full wipe and re-install. A Factory Reset using Android Settings options would be the equivalent of leaving your Windows install untouched, but deleting all of your personal files and hoping that fixed the problem - it accomplishes nothing if the problem didn't start with a specific app or a change in settings to begin with. VZW has technicians in stores where repairs are performed that *should* have training and software capable of performing this task, it is NOT something a customer with little technical knowledge can do from home without research and the proper tools.
That said - you can find step by step instructions on how to flash a factory ROM with ODIN online. But it is not something I would really tell a customer they should do since there's always the possibility of 'soft bricking' your device in the process.
I would first try to talk to an actual repair tech at the store, rather than a sales associate or customer service rep. They may be able to better understand what it is you're asking for. If that doesn't get you anywhere, you're always welcome to join any of the various development communities and learn how to hot rod your phone. 
