The OP may be lying. However, I've experienced something similar.
I was recently banned for buying an Inscribed Red Fan for 4000g through a trade window.
I even appealed the process and was given an automated response stating that they still believed I had been buying/selling gold and/or botting. They would not undo the ban.
Only after being persistent in asking for further proof of my accused offense did they have someone actually look into it. Turns out you can be a 'false-positive' on their automated banning process/program.
Guilty until proven innocent.
I hope the OP can do something about his situation. Blizzard will more than likely win. Good luck.