David,
Shutting down phone service for non-payment of advertising doesn't happen anymore. They used to do it when the phone company was Ma Bell in the 60's. Today the baby Bells just sell "bad" accounts to collection agencies that hound and harass till they make you bleed.
A plumber buddy of mine is in the same boat and they told him they won't shut down service but will kill his credit and sell his account to collections. He told them he was joining up with another company and didn't want the ad anymore, they told him tough luck. Until the $7800 bill + interest is paid no more ads for anything he's connected with. They do a dun & bradstreet and several other credit checks to follow up.
The way they catch people too is with signatures, if you sign the contract you are liable for the amount due, it's a legally binding contract. If you don't sign it they have you on tape agreeing to the ads, binding you. Ever listen to those on-hold phone messages when you call, "this conversation may be recorded for training purposes." Yeah, to train the dogs. The small ads like name and numbers often get automatically renewed by sending the paperwork to you. Read the back, if you don't come right out and tell them you don't want it, it's automatic you got it, with a hefty increase in price, I might add.
Here's another kicker, if your ad is wrong - they will apologize profusely while telling you to pay up. NEXT YEAR, they give you the free ads, you hope with corrections. They project profits and want that pound of flesh now.
The real phone companies, SBC, VERIZON, SPRINT, MCI don't screw around, trust me, I have felt their wrath and done the research. The up-starts like YELLOW BOOK, etc. are less vindictive because they are trying to woo the big guys customers.
Bottom line, don't wash into the wind and don't screw with the phone company.