There is a great Snopes page about this:
There used to be another web page back in the 90s. Some guy called the number in every area code and had a table noting the results. Lots of not in service, lots of perfectly normal answering machine messages, and lots of messages to the effect of "If you're looking for Jenny, she's not here." There was also one "You've reached Jenny, please leave a message" in an obviously male voice.
I read an anecdote from a young adult author years ago. Can't remember who, unfortunately. He had to include a phone number in one of his books - I don't remember why it had to be included, as opposed to just "He gave me the number" or whatever, but art is a fickle mistress and is best not denied - and he didn't want to use a fake 555 number but he also didn't want to annoy the snot out of some poor sap with the misfortune to have the same number. So he used his own phone number, area code and all.
His family apparently got a fair few calls from fans, and they were happy to talk to them. They even talked a few kids through some tough times, which must've felt good. Eventually, though, he came to discover that his teenaged son was accepting collect calls from fans, and it was adding up. So he reluctantly changed future editions of the book. I don't remember exactly how, but after that they no longer had his own number in them.
I'm pretty sure it wasn't Chris Crutcher, Daniel Pinkwater or Stephen King, though those are the names that pop into my head when I think about authors who might have done something like that. It's gonna bug me now.