How to report someone on your friends list for suspected elo boosting?

Just as the Title says, I have seen multiple people blatantly do it you can even see their summoners change normally Flash-D Ignite-F but swapped around for X amount of games of wins and then plays normals but has the summoners the other way around... They will mysteriously jump from low silver/bronze to like Plat 4 and then play almost no ranked at all for the rest of the season. I just wanna know if there is a way to report these people or if I just leave it up to rito to figure it out.
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