How to promote to Samurai with Boost

[iMemphis]

What class was your retainer before your boost?

Also, what was your starting job?
GNB, DRK, and SAM are all jobs you have to unlock. What did you choose at character creation?

I believe I created a lvl 7 warrior. Then boosted to DRK long time ago. My retainer has the option to become a warrior, but since i am only lvl 7 with it, her max level is 7.