Return to the master outside of Khal. He'll send you off to meet the two masters of the style that you're not currently on. Once done with that, you loose your style and can choose a style of your liking.
The quests are repeatable ad infineum, so you can pick back should you not be happy etc.

hey someone let me know what the name of that guy in khal is again... I am already dragon but i might want to try some of the other styles out there