Unfortunately that's the risk you run across when frequenting the exchange...people get pissy when they realize they sold for a lot less than they could have, report you, or you buy a hacked item or botted item.....
Have you filed an appeal yet? If not, I would suggest contacting a mod and see what to do about getting the ban revoked.
I sold my Demonic Anklets for 30k like last year, on my first account made..and I didn't report the guy when it went up to 50k, then 70k like now.
EDIT: I meant last, last year, in 2007. I didn't realise it's 2009 yet, it takes a while to get used to a new year, I guess.
30k? eek I've never seen it at that price. I got mine for around 48k.