Your mistaking your ban from a leavebuster ban. The leavebuster ban infact gives you restriction on games, you would have to leave about 5-6 games to get a ban; consistently.
http://boards.na.leagueoflegends.com/en/c/miscellaneous/EZbHLGZY-introducing-the-new-leaverbuster-system
As to your restriction, I was also a victim of chat restrictions, and I was restricted my self. I knew I was toxic, and I wanted to reform, but they send me a automated message. I'm sure you got something like this.
"Hello Name,
While the Tribunal is in recess, we're unable to provide specific chat logs or reform cards for chat restrictions. I'd be happy to help clarify what's going on but it's important to note ahead of time, we will not be removing or reducing the number of chat restrictions placed on an account
We've investigated your account and found higher than average levels of toxicity as a result of your actions in the matches you play. As a result, we have decided to place chat restrictions on your account to help you adjust your behavior in-game.
Our chat restriction system is in place while the Tribunal is currently in extended maintenance while the Development team works on improved features and enhancements.
The chat restriction system works by analyzing recently played games on your account. This doesn't take into account the amount of time that passes between games, which prevents players from simply waiting out punishments. Additional chat restrictions may be placed after your first round is complete if there is no visible improvement in behavior. It's possible to receive punishments harsher than chat restrictions should toxic behavior persist (including temporary and permanent suspensions).
It's important to remember that there is no excuse for being rude to others. If you think other players are intentionally trolling, then be sure to report them at the end of the game. Arguing with them in-game is rarely an effective tactic. If you're having a bad game, insulting your teammates doesn't help them improve, and it won't help you win the match. If you're not going to say anything nice, don't say anything at all.
If an argument is getting heated within the game, you have a few options. You can hide [ALL] chat, mute individual players, or move the chat box away from the screen. You can also try re-binding the "Enter" key to something else, or remove the "chat" binding entirely.
For more advice on keeping to the Summoner's Code, check out this article:
https://support.riotgames.com/hc/en-us/articles/201751874
And you can learn more about chat restrictions here:
https://support.riotgames.com/hc/en-us/articles/201752984"
Simply type back to them and it will be a real Rioter to tell you why you got muted/banned. Make sure to read those articles, however. In the meantime, try reading these.
https://support.riotgames.com/hc/en-us/articles/201752924-Behavior-Alerts-FAQ
https://support.riotgames.com/hc/en-us/articles/201752714-Leaver-Buster-FAQ
