If you suspect your opponent of unfair play, you can note this during the game by clicking on “three dots” icon to the left of the board, and then on the "Report" button. You’ll be asked to fill in a short report form. Choose “fair play” in “what would you like to report?”. If you didn't manage to report via form, please contact support@chessarena.com and share the details and png of the game you consider unfair.