in your main menu in the game you will see a section called "System," scroll all the way to the top of that section to where it says "Support Desk." from there go over to "Contact Us." once in there scroll down to the "Report Cheating" section and then fill in the form with all the relevant data that you can remember about the incident. Once that is done hit the submit button and from there the impetus is on the Games Staff to deal with the issue.

This is all based on the assumption that the individual is a bot. The easiest way to confirm whether the individual is a bot however is to try to send them a /tell message asking if they are stuck or what not and waiting to see if they send a reply to you asking for assistance.