Playing Online: You can’t unregister a game. You can join the game before 3 chance skips and if you don’t you are made to leave the game and your rank will be calculated based on the order in which you leave the game.
Playing with Friends: You get an instant refund if you leave the game before it starts. If you are the creator of the table, everyone who joined will be refunded their entry fee as well and the table will be cancelled.