You are not officially in any billet until you graduate from OSUT (EVERYONE must attend OSUT). On Day 4 after your FTX, your instructor will give you an opportunity then to decide on a billet. Even after that decision is made it is not set in stone, and transfers will be available later as well. Do try to think about it between now and then, because if do decide to transfer later, there are penalties to transferring more than once every 30 days.
