I'm trying to find a copy of a short film
I saw in the early 60's that I think was
based on a Bradbury story. The film is about
a man who gets strange phone calls of electronic gibberish. The calls continue and the gibberish becomes an electronic voice
that repeats whatever the man says. He eventually traces the calls to a relay and is electrocuted when he checks it out. A phone company worker closes the relay without looking inside and the implication is that some sort of artificial electronic
intelligence was lurking within. It was
utterly creepy and believable. Does this sound familiar to anyone?

See answer below under the topic "Dial Double Zero."