Murder by Phone

Murder by Phone is a 1982 science-fiction slasher film directed by Michael Anderson and starring Richard Chamberlain, John Houseman, Sara Botsford, Robin Gammell, Gary Reineke and Barry Morse. Its plot follows a series of murders committed by a disgruntled phone company employee who designs a device that kills victims when they answer their telephones.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.

Poster © the film's rights holders.