This happened to my dad, but he used to tell us this crazy story about some weird phone call he got while working as a security guard. He was working the night shift at an abandoned hospital, which he always said gave him the creeps, my dad's name is Robert. He is a tough guy, no-nonsense so I know he was not lying. 

So as the story goes, he was doing his nightly walks around the parameter, as he approached the back of the building, near the old ambulance entrance, he swore he heard a phone ringing in the old emergency room, As he went to investigate, the sound got louder and then suddenly stopped just as he flashed his light around the room, this was some spooky stuff. To this day, he still cannot explain the ghostly phone ringing in the abandoned hospital that night.