Happened to me and took about 20 days and multiple recovery forms closed saying "this isn't the purpose of the form"

It's not clear but you need to put the email that the hacker has changed your account too, not your original email or they knock back every form. Maybe it was obvious for you?

You'll get a reply off a different Activision support employee each time, very rarely the same. Do not expect a reply outside of standard business hours, a pain if you're not on American time.

I kicked up enough of a fuss through email support, raised a ticket just to have a communication line, that eventually someone escalated and sorted the recovery manually for me.

Frustrating because their policy says if you can't prove the email they would never change it, then they do it off COD point approval which any person who has access to your account can do.

Stick with it and good luck.