Riot, i'm trying to report an ELO Booster (I think), what do i need to show and to who?

a guy sent me a friend request a couple days back, I accepted it cause what the hell, you can't have too many friends. Anyway, they are always offline, but after every single game i've played since, a message from them pops up:

"You know what isn’t good? High blood pressure and losing games gives you that. Getting and ELO boost will help with that." [followed by a link i haven't clicked on yet]

I have a screenshot and the guy's name, just need confirmation that it's something they shouldn't be doing and what information Riot needs to stop it (if it needs to be stopped).