what can i do against a toxic premade?

I just played a game where a kayn shaco and cho (on my team) were shit talking us(blitz and me) all game, and at the end they just played cool with the other team and even after blitz and I reported them I realized they aren't getting banned because the enemy didn't know they were toxic and just 2 players cant get 3 people punished for toxicity, so I want to know how do toxic premades get punished. I have been playing for 4 years and still don't know what to do in that kind of situation.

I suppose one option is to mute them but that won't change their behavior and I just want to know if there is anything I can do to help punish toxic players because it feels like whenever I come back after a break I just don't feel like playing anymore after dealing with people like this.

Sorry if I sound like I'm complaining but I don't see how people are allowed to get away with stuff like this.