Active and Inactive heroes

[Demetrie3_9385695]

there should be a way to trade out active and inactive heroes from hero inn to formation. I'm stuck with all these heroes from where i was sergeant, now I'm a major and I can't use any of these newly unlocked heroes because i "as I already have 12 active heroes" >=-(
I can't use Shayd, Saffron, Valla, Calvin, Cianna, Alexa, Ahmose Nekhbet, Hypatia Alexandria, Thucydides, Knight Percival, Jeanne d'Arc, or Themistocles. I have everyone of them but I can't use them because i already have 12 active heroes. I suggest it be changed. It's freakin bullcrap I can't use these