This is a flock call because he is so bonded to you. My 'tiel Coco does the same thing to me. You can't really stop the flock calling as such. What seems to work best is to ignore his screaming until he calms down (sometimes it takes a while), and then reward him with a head scratch or a treat for being calm. You can call back to him from the other room but this tends to just prolong the flock calling.