The title was Deadline, Deathline, Phoneline... Something like that. But nothing I search for turns back the right book. I remember the cover having an old candlestick style phone, and maybe telephone poles in the background. There might also be a coffin, maybe in the background. The story was set in maybe the 1970-80s.
I read this book as a CD-based audiobook as a kid (2000-2005ish?), and it was way WAY out of my depth. Picked it up from a public library, and it wasn't new by any means. I recall weighing the choice between this book and The Invisible Man by Ralph Ellison; ironic that the one I remember isn't the one I read.
The protagonist gets a job turning off a light switch as soon as the bulb turns on. He gets paid a lot, but it's very boring. He makes wheels for his elbow so he can hit the switch faster. At some point he looks into the situation and finds he works a kill switch for a phone line/booth that can call the dead.
It goes really off the rails from there. I remember a reanimated woman who's not quite a zombie. The main character, this almost-zombie, and another guy are on the run, or otherwise moving around a lot staying in motels. They're some strange love triangle between them, but I don't remember more than that it was kinda graphic.
The protagonist somehow makes an enemy, that might be a demon or spirit? Something supernatural. The book ends with the protagonist and this enemy, body swapping with random people all over the world... so they can hunt each other down, kill each other, then randomly body swap again. It's some kind of stale mate solution to their conflict.
There was an old joke some side-character told that had someone seeing a sexual situation in every Rorschach blot. When the doc points this out and says they have a sex addiction, they reply "Well you're the one with all the dirty pictures!" (I heard this joke years later in a totally different setting and thought they got it from this book, but turns out it's a pretty common one I guess.)
There were some rules about the phone line. I think you could only call a dead person once, and there was a strict time limit. I think he calls his father, or grandfather, some patriarchal figure. The protagonist breaks one or both of the rules, and I think that's what puts them on the run.
Thanks in advance