Was banned for having a 4 man premade troll me by not remaking when there adc friend was afk.
I was support and he didnt join the game for 10-15 mins plus, they flamed me for wanting to surrender and griefed me
That won't result in you being punished.
I was toxic as well
That's what you were punished for. If someone else is being a jerk, don't stoop to their level! Muting players is a powerful tool to mitigate harassment in chat, and reporting players is how you get them punished so they don't continue acting this way (if they are like this frequently).
You can submit a ticket to have player support look, but typically they stand by the Instant Feedback System's decision, as it takes regular and/or extreme negative behavior to get punished; this wouldn't likely have been the result from one or a few games. If you want to discuss the chat logs you're free to post those here.