You can use our !calladmin plugin which alerts staff members even when they may not be in-game. You can also submit a server report on the forums containing the evidence and it will be reviewed by our staff.
If you believe that someone has just left the server without paying after a wagered spycrab or heavy box, you can report the user over here. Make sure to provide as much evidence as possible. Gather your evidence of the scam, including screenshots of chats and inventory history.
Yes, if you have been scammed outside of our servers, you can still report on our forums. However, we cannot mark the accused if scams involving trades occurring entirely outside of Steam trading has happened. Although we may not issue a ban on SteamRep, we can still accept these reports and we may issue a server ban. For more information, read this thread on SteamRep.
If you believe that someone has posted something inappropriate on our forums, you can use the report feature. On the thread/post, there is a report button. When reporting someone, please make sure to clearly state your reason.