Once picked you can't change them. Classes will rank up at Level 45.
1st Rank Warrior ⇙ ⇘ 2nd Rank Berserker Paladin
1st Rank Sorcerer ⇙ ⇘ 2nd Rank Sorcerer Mystic
1st Rank Archer ⇙ ⇘ 2nd Rank Hunter Ranger