@Riot How to report a player who added me to offer to boost me?

Had an account I didn't know add me, so I accepted it to see who it was and instantly got a message of "Get Your Season 7 Rank Right Away With Our Placement Boost At www.(removing to not promote them).com !!!10% Off Until December 14th!You can also do your placements with our DuoQ service, just choose your Season 6 rank!" and then they logged off. Is there a way I can report this account even though I didn't play a game with them? http://imgur.com/NsrttB5

Edit: added screenshot