I'm sorry this happened and I hope you can get your phone fixed.
I second that sorry as well. I hate to say it, but from what I have read and researched, when Knox prevents a bootloader change, it is the ultimate brick, as in not even a JTAG can fix it. Very crappy, and I think Samsung is going to take a small hit in the future from previous owners who move away from them the next time a device update is in store thanks to the garbage known as Knox that was forced on a lot of unsuspecting device owners.
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