I am not complaining for the other two strikes on my account (though really getting banned for accidental team kills on grifball? This is besides the point though) I received my 3rd strike after lagging out of the lobby I was in after the actual game ended, so I could have pressed B to leave but since I lagged out it added another strike to my account. This is somewhat ridiculous, since I had the option to leave and this would not have hurt the game play of others.
There is a pinned thread in the Support forum for discussing bans:
Please go there when posting about bans you have.