That is line of sight screaming... when you are out of sight, the bird gets nervous and calls to you. It also has a component of, your bird is attempting to train you to come when you are called.
Line of sight screaming stops when the bird can see you...
So if you move the bird around with you and he can see you, it stops. Which isn't always practical.
Basic screaming behavior mod. protocols are as follows:
Cover the cage on 3 sides with a cover when the bird starts screaming.
If the bird continues to scream, cover the 4th side of the cage.
The bird will quiet down when he is covered. (It is also sensory deprivation.)
As soon as the bird remains quiet, uncover the cage, and praise him for being a good bird.
REINFORCE THE GOOD BEHAVIOR - DON'T JUST PUNISH THE BAD.