My characters disappeared after I bought more hero slots (PS4)

So I was buying hero slots so I could have more heroes so I bought two more slots with my defender medals then I went to make a wizard and it deleted my squire then I made a new squire and it deleted my ev2 and finally I made a new ev2 and my huntress disappeared and now all my hero slots are full now and I haven't used any of them because I'm still stuck with four characters. All I'm left with now is a monk which is useless without all the characters I've lost please notice this and help me.

@RIOTZWizard quote:

So I was buying hero slots so I could have more heroes so I bought two more slots with my defender medals then I went to make a wizard and it deleted my squire then I made a new squire and it deleted my ev2 and finally I made a new ev2 and my huntress disappeared and now all my hero slots are full now and I haven't used any of them because I'm still stuck with four characters. All I'm left with now is a monk which is useless without all the characters I've lost please notice this and help me.

Did you watch the tutorial videos?

No

Inventory > L1> L3 to open your full hero list, then L1 + dpad direction to set a hero as active.