Possible Ban Evader on my account

Hey not sure if anyone can do anything about this but just wanted to ask. It seems someone had been using this account for the past couple of days and trading on it with other sythe members. very strange. I realized as I logged in today and saw P.M.s from people I never messaged and this thread http://www.sythe.org/private-server-gold-items-misc/1944644-selling-os-scape-gp-cheapest-rates.html that the person made. Another thread that he created: http://www.sythe.org/oldschool-runescape-buying/1944269-buying-rsgp-trusted-1-1-2-m.html Doesn't seem like he scammed anyone yet and he uses a fake Darkpk skype in order to trade with others and it is under the skype username: dclawsownage
This has never happened to my account.. My password has been changed if anyone can give me any tips on what I could do now. Feel free to. Not sure if you guys can see his I.P. and match it to someone else not sure why someone would grab my account and begin to legitimately trade with other members.

 

Those are threads you created.

Please remake your report following the format on this sticky, because I'm very lost:

http://www.sythe.org/report-ban-evader/1240795-read-template-reporting-ban-evader.html