If you imagined that the Big Apple has cornered the market on obscene or harassing phone calls, guess again. And the next time people begin swapping "perv" stories, think about this:

The business offices of the C&P Telephone company of Washington receive an average of 800 calls a month from customers complaining of abusive or annoying calls. In fact, the volume is such that C&P has a separate office to deal solely with that problem. But you can't reach the Annoyance Calls Bureau by phone. Instead, you must contact a C&P business office, which relays a form report to Annoyance Calls, and they in turn get back to you.

This usually takes a couple of days, particularly if you've had the bad luck to receive a series of obscene calls late on a Friday afternoon. In 50 percent of these cases, by the time the Annoyance Calls Bureau responds to your complaint, the calls have stopped.

It's a federal offense in the District to make obscene or harassing calls. The penalty is a $500 fine, six months in prison, or both, but the nuisance caller who selects your number at random, calls you once or twice and never bothers you again probably won't drive you to change your phone number.

Which is the next thing the phone company will suggest. If you do want your number changed, the phone company won't charge you for it, unless of course you want to have it unlisted or unpublished the next time the new phone books come out -- that'll cost you 40 cents a month.

While a nuisance is just that, the persistent caller, the one who disrupts your peace of mind, is another thing entirely. District police say they routinely receive requests for assistance from the victims of abusive calls, but unless the calls are clearly of a threatening nature, they'll refer you to the phone company first.

If the calls persist, C&P will put a trace on your line and keep track of your incoming calls, but it needs written permission from you to do that (another form), and only about 8 percent of those original 500 callers actually get around to granting it.

The phone company says it can trace a call to just about anywhere: a rooming house, a restaurant, even a pay phone in another city. Once they've discovered the number, they will make a "deterrence" call, informing the owner of the phone that it is being used in an illegal manner and taking care not to accuse anyone of anything. They also explain that if the calls continue they may be forced to terminate service. But the phone company can't do much more than that, which is where the police step in.

C&P's security office and the police department work closely on threatening-calls investigations, although the relationship, in post-Watergate Washington, is more formal than it once was. To obtain the phone company records necessary for an investigation, the detective assigned to the case must have a supoena, which means a trip to court.

Some investigations take months to close, others as little as a week.In a recent case a Washington woman, frequently out of town on business, was being plagued by as many as 35 abusive calls a week, left on her telephone answering service. The calls were traced to a pay phone, but it wasn't until the woman began receiving threatening letters that the police had the evidence necessary to arrest their suspect -- his fingerprints were all over the envelopes.

Most of the time a threatening caller is not a stranger to his victim. Several months ago detectives discovered the source of a constant stream of obscene calls to a young woman's apartment was the apartment right next door. "Grudge" cases, where the caller is a business associate or an ex-boyfriend, are also common.

Depending on whether or not you think a jail cell is the best place for a "perv," you will be encouraged or dismayed to learn that most of the time a police investigation of a threatening-calls case does not result in a conviction. Most cases never even go to trial. Instead, the preliminary step, the issuance of court summonses to both parties and a hearing before the assistant U.S. attorney, is the last.

This is because the suspect, usually a male in his late 20s or early 30s, frequently confesses guilt once confronted with the evidence. In most cases, he is a first offender and a confession earns him unsupervised probation. If he stays out of trouble for the next year there will be no criminal record of the case.