If you've completed the quest including the level 70 one, then that's all there is for now, the quest chain ends at level 70. Presumedly when the next expansion rolls around they'll add new quests but for now, 70 is the final one. If you haven't yet completed the 70 quest however, then all I can suggest is search your Journal and see what it says (turning on the Duty List can also help, as clicking on it's objective will open the map with an indication of where to find the NPC in question). Sadly I've only done the first SAM quest to unlock the Job, and for that the NPC was in the GLA's Guild (at the stairwell down into the Colosseum arena), but he's almost definitely changed location during the quest line.

Another possibility is you may be missing a step in your objectives, in which case checking your Journal is doubly helpful.