How to report someone out of client

Hey,

I got a OTP master yi who forced me to dodge a game because he was going to troll. I took a screen before dodging the game, i've been forced to dodge 3 games in a row and am now at -10 points. It's kind of getting on my nerves and I'd like to see these people get punished for their actions. I have a screen I can send, where he says "I troll" and goes and locks Soraka support.

Thanks for the help :)