Reporting For Sending Messages to people for BOOSTING!

So it happens quite often, and i dont know how to report people unless its right after a game and reporting for gameplay things. but, people send me friend requests and i thinks its someone i have played a game with recently and it says this** "Hey. I was the person from earlier. I was boosting. I thought you might be interested since its cheap atm [REDACTED];** 8:26 am is this reportable. i can also say. that i dont think a person did it himself. i think he set up some kinda bot to do it because as i accepted the friend request this message popped up to me about 0.5 seconds after. PLZ help because we dont need this is the LoL Community....