Blood Elf Warlock can't find quests for pets

I am 28 lvl now. But I still can't get voidwalker, Succubus. First time when i got imp, I couldn't finish the quest for imp, so i decided to buy it instead. Then i realized that i cant find voidwalker and succubus quests and my master don't have it in the spell list. I looked for some info about my problem and couldn't find a reason why cant i get them. I checked the locations where quests supposed to be, but still nothing. What is wrong with Blood Elf Warlock? I don't wanna create another warlock, and i am not sure it will help.. Can anyone help me with that?