Keep in mind that I've NEVER actually had to unroot, so I personally can't verify any of this, but here is the post on how to un-root (see bottom of first post starting at "back to stock")...
http://forums.androidcentral.com/ve...ck-bootloader-verizon-galaxy-s3-sch-i535.html
OK -- this *may* not be the solution for everyone, and does require getting one's hands dirty. If you are really uncomfortable doing these sorts of things AND your phone isn't rooted, then Verizon customer support should help you...although their solution will probably be to get you a new phone. To me, this is pretty straight forward, but I realize that may not be the case for everyone...
See this guide from over on XDA:
[GUIDE] Jelly Bean Factory Image (Root/Recovery/Unlocked Bootloader) *UPDATED 12/12* - xda-developers
By completing ONLY step 1, you will have installed the latest official version of Jelly Bean. As this is an "official" image, it does not require root and is not *technically* a violation of the TOS either (Verizon would not be able to tell if you did it this way vs. the OTA). If you wanted to take it further and complete steps 2 and 3 to root an unlock, that's up to you -- but at that point you would be voiding your warranty.
As it states the only modification made to the stock image being used in this method is that it doesn't wipe the internal data...so it will, in theory, allow you to keep your apps and settings similar to installing an OTA update. Since I, again, have not personally used this method, I will float 2 additional caveats out there...
1. Always be aware that there is chance data could be lost in the process -- make sure your contacts are synced in Google, and backup what you can/want prior to starting.
2. I have found that whether it by OTA updates or manual flashing, a lot of updates are simply more "error free" if you do a factory reset prior. That's a real PITA, so most folks will take their chances and not do a factory reset unless they *have* to (and I understand that), but just thought I'd toss that out there.
For those not familiar with use ODIN, it's a standalone Windows executable that can be used to flash OS images to your device, here's a brief how-to I copied from another post: