Ok I left a couple of matches and I know that after a couple ill get a leavebuster ban and the first time i got it i got a warning about it ok. Now that we got that out of the way the second time i got it i got notified again. This third time im getting banned without and i dont understand why you guys wouldnt warn me about it this time i am very angry at the moment because i was looking forward to playing LoL but then this happened with no signs of warning or any pop ups. Would you guys please explain this problem to me?

It have a "cooldown" on the levels.

First time you are in trouble, it will give a warn.
If you play enough without leaving, it will clear the warning.

Since it was clear, next one would be a warning again.

But this time, you did not play enough games to lower the cooldown,
so it went from warning to ban.

You really have to avoid leaving, not only to not get banned, but it hurts your team.
Here is more info.
https://support.leagueoflegends.com/...ver-Buster-FAQ

Thanks buddy

Please keep in mind that leaving games is not acceptable behavior in League of Legends. When you leave a game, you put your team at a significant disadvantage and likely ruin their experience. For this reason I recommend having at least an hour of time available before playing Summoner Rift. (It's rare for a game to last an hour, but it can happen on rare occasion.)

We know that from time to time despite your best efforts you may need to leave a game for a reason out of your control: emergencies and internet/hardware issues happen to everyone at some point. For that reason Leaverbuster doesn't punish you for a rare leave. As long as you continue to play more games without leaving, your account will be put back in good standing again. However, repeated leaving is not permitted and will lead to increasing punishments.

Just keep playing without leaving and you'll have nothing to worry about

Took the words right out of my mouth, both Kinvaras and the Riot person.