I have seen that much ppl are asking where to do the 3rd jobchange.
Here we go. You need to be lvl 85, and when u will reach that lvl go to PUB (Pub Of The Giant Bird).
Klick on the man that is called All Jobs Teacher (or something like that
).
Ex. if u are Expert Archer just click that u wana be Imperial Commander and go learn Imperial Commander skills.
Now u have bots jobs skills