Players with second accounts trying to keep their ELO low

Hello, Please read this with an open mind. Thank you. This is the first time that I am posting here. I play in Silver 4, and I do believe that my rank corresponds to my game skills. However, as of late, I have noticed a trend that is baffling me, and makes me frustrated. I've seen players who are very good, and should be in a much higher rank (game play, understanding of game mechanics, very precise moves to attack or dodge, AA canceling of the opponent … ). They play really well until mid game. Then they suddenly go AFK farming of the jungle. Suddenly, the team has lost half of its kills, and now the game is 4v5. You can imagine what happens next. You lose the game.

I have read some of the other posts here, and some players don't want to believe what I have written in the above paragraph. But please, have an open mind. I have saved the recording of one such games, and I also have screen shots of a player (Which in this case was in the other team) explaining to me why he went to afk farm. In his words: "I wanted you guys to win, I don't want this account to be promoted". I spoke with him a bit longer, and he told me that this account was his second account, and that his main account was in a higher ELO (again, his game skills showed).

You can also see the trend by looking at the history of the said players.

I don't know what the remedy to this type of behavior or action is, but I can tell you that it is very frustrating to lose a game like this. Specially when I play as support a lot (Let's be frank, not many people want to play that role, and I rather to be the support instead of forcing someone else).

Thank you.