I dont think that you should call for helpers here. Try getting a moderator thats online. Most of the time there is a couple in the lobby hanging around, and you can find them there to ask them about this. You can also record the hacker and report them in report abuse under hacking, cheating, and glitching.
Calling a moderator isn't the right thing to do -- You can record him and report him at http://itsjerryandharry.com/forums/hacking-cheating-glitching.33/ For recording, Bandicam fits my needs -- You can get it from www.bandicam.com/downloads/ It's free and good