A film on reel to reel I watched in 7th grade history. Been haunted by it off and on since. The "voice" starts talking to someone early in the film, repeating hel-lo back to the person on the other end. The entity, for lack of a better word, seems to call other phones and learns to speak better as the film progresses. The clear implication at the end is that the entity has decided to infiltrate the phone system at the White House for God knows what reason!