My faction was switched to Knights from Samurai

so i just launched the Gold Edition of the game, and to my surprise i am now part of the Knights faction and not the Samurai, i was part of the Samurai Faction during the closed and the open beta, and now when i want to switch back to my faction of choice, i am threatened by a message "Changing factions will remove your rights to receive faction war rewards related to current round.
Seasons rewards will also be lost if change after first round."

how can i change back to the Samurai faction without losing my rights?