This is my #1 advice to you if you are trying to climb elo like me.
DON'T FLAME.
I get it. Your bot lane is feeding out of control and you're losing grip of the game. As you're about to spam some nasty insults to them, please reconsider. First of all, they're probably just having a bad game and/or are probably on tilt. Flaming them will not make them any better, only worse. I understand the urge to vent your anger, but doing so will just only result in a less fun game.
If you played a game and you knew you performed your best and lost, there's no reason to be salty. If you are performing well your MMR will slowly rise. Just stick with it and be patient.
Be nice. Be supportive. Give advice.
We all have bad days.
"Stay positive!"