I suck at everything and am no trainer. But I did "cure" a hardcore screaming HH of screaming.
Yes, screaming is a contact call. I used that. My bird was given to me because even though she was a proven hunter, she screamed her darling lungs out at the sight of any human, neighbors very much included.
I picked her up, and having been a cockatoo owner, I thought I was ready. She screamed the whole 5 hours home. Out loud, in Technicolor.
So when I got home I tried to figure out what was wrong?