I want to report this person

I played against this person 2 times (casual),

first time he won RPS and has chosen to go first, at the very moment I started having the advantage in the game, he said: Yawn and disconnected.
So I joined the queue to play again, and was joined against the same person (unfortunately),
Again he choses to go first, and at the very begging of turn 2, I summoned Levianeer to destroy 2 of his cards, he gets mad again and says: “not you again Sigh” and left the game.

I feel like this childish and rude behavior will piss off anyone, not just me, and this person should get a warning.

There’s nothing insulting here. A “sigh” is not enough to warrant any bans.