Please tell me you're joking.
If you started your first character on a warlock, you were stuck with void walker until you reached level 15. Then you unlock your second subclass (sunsinger).
If you started on a hunter then you were stuck as a gunslinger until you reached level 15 to switch to bladedancer.
If you reached that level on one character it unlocks all the other subclasses on other characters when you start them.
My point being, Hunters started off with a solar subclass, warlocks didn't.
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I was able to switch pretty early on my first warlock before hitting 15.
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Then they changed it later or you already had another character to level 15 before your warlock.