All devices are different in many ways. What is perfectly safe to do with one brand or model can brick another.
And I wouldnt call it "bad" advice... I've seen audit13 and others helping lots of folks with very good advice. We all make mistakes and we all have more we can learn about these devices. No one knows everything about this stuff and shouldnt let that prevent them from trying to help.
Those who are trying to help are doing so with the best of intentions and tell people what they think could be the best way to solve a given problem. In cases like this one, its easy to see how anyone would think its ok to flash different firmware between similar models based on being able to do so on other devices they are familiar with. (If I had gone into those forums I wouldve been telling people the opposite and ended up being wrong there.)
All I can say is chalk it up as a new lesson on a different device, and I hope you still appreciate that someone was trying to help.
I hope none of this discourages you from helping. Ive seen plenty of threads where your advice was sound and appreciated, and I am glad you have been around to help so many people out!
Now, back on the problem at hand... if you want to be running the latest 4.4.2 kk, you will have the option to use the OS (/system and kernel) from either the I747 or I747M firmware. But first you must fully update to a minimum of the 4.3 MJB firmware for the I747. Once you have this running for your base firmware/bootloader, you can then run the Bell or AT&T (4.3 or 4.4.2) system. (I hope this is making sense!)
So first, update the full 4.3, MJB, firmware via Odin. (Theres a thread in General with the file, ill post the link in a min).
If you want to update to 4.4.2 firmware, you can then follow enewman17's tutorial to do so via OTA.
You can then either stay with that, or use Mobile Odin to flash ONLY the system and kernel from the Bell firmware.
Let me know if any of that needs better clarification! Also let us know what your ultimate goal is. From the options you have, where do you want to end up?
---------- Post added at 10:32 AM ---------- Previous post was at 10:26 AM ----------
Ok, here are some links.
Stock MJB firmware (flash in Odin)
enewman17's thread for updating to 4.4.2 (high success rate)
Official, unmodified 4.4.2 OTA
After updating with the 4.3 firmware, you can first try using the official ota to update. Then, if that fails you can go to enewman17's thread and try his method.