Exclamation [Q] [IMPORTANT] AT&T Samsung Galaxy S3 in a Boot, Loop. Help!

(*Here's how the whole story started.)*So I recently wanted to update my Galaxy S3, and for some reason the Baseband Version was different from other AT&T Galaxy S3 Devices. So, after I brought it in to Best-Buy they said they can't fix it, even though I contacted Samsung and they told me they could flash it with this ''SMART'' Tool (Which Probably is Odin3) Rooted or Not. I was tired of trying to fix this because, I was on 4.0.4 Ice-Cream Sandwich, and my friends bragging about the 4.4 KitKat Update they received. I literally tried everything, from clearing the Google Services and the AT&T Software Update on the Application Manager. I had the Baseband Version: I747UCLF5. I was tired of not getting the update, so I just flashed the Original ROM from Samsung-Updates, using Odin3. Samsung-Updates had only 4.1.1 Jelly-Bean, so I thought about just updating from Jelly-Bean.*
(*Here's how the Samsung Galaxy S3 wouldn't turn on), and was stuck on a boot-loop.)*So, continuing the story, I successfully updated to 4.1.1. Jelly-Bean. So, when I was on the 4.1.1 Jelly-Bean I checked for updates, and I successfully updated to 4.3 Jelly-Bean. Yes, I know that the 4.4 Kit-Kat update was out, so I continued updating the phone via OTA. When it finished, it started updating with AT&T Logo on top and the Percent with the Bar on the bottom. After it reached 100%, it was rebooting crazy. The Samsung logo went on and off and the phone went vibrating every second. I'm pretty sure my power button is not broken and when I put it in Recovery-Mode the same updating process came. (AT&T Logo, Loading Bar with Percent and a message saying ''Updating...''). Ever since that day, I re-charged it and I put it in Recovery-Mode, and same thing happens and when it finishes it's doing the boot-loop. I tried putting it in Download-Mode and tried to flash it with Odin3, but it didn't work at all. It had this error message. I'm pretty sure the Boot-Loop is caused by a Locked Boot-Loader. This is What it says in Download Mode.

ODIN MODE
PRODUCT NAME: SGH-I747
CURRENT BINARY: Samsung Official
SYSTEM STATUS: Official
QUALCOMM SECUREBOOT: ENABLE
Warranty Bit: 0
BOOTLOADER RP SWREV: 3

Please try to help me with my situation. I am currently using a older phone, and I am desperate of getting my phone back. Thanks! Anything will Help!