Coinless public telephones are coming to the Washington area and customers won't need the customary 15 or 20 cents to make a local call.

Instead, it will cost 40 cents per call for the caller who otherwise would plunk 15 cents into the ordinary variety of pay phone in Washington or the Maryland suburbs. The Virginia caller, who can dial from a coin-operated pay phone for 20 cents, will be charged 50 cents to call from the coinless variety.

Billed as "part of the trend toward a cashless society," the phone company says coinless public phones are not intended to replace the coin-operated variety. They are meant primarily for businessmen and travelers making long distance calls by using credit cards, calling collect or charging calls to a third number, a company official said.

Al Wann, public relations director for the Chesapeake and Potomac Telephone Co., said local call charges from coinless public phones are higher because they require an operator's assistance. He said regular coin-operated public phones will be located near the coinless ones for those who prefer to pay 15 or 20 cents rather than 40 or 50 cents for a local call.

Nevertheless, Richard Cuffe, a deputy general counsel for the U.S. Office of Consumer Affairs, called the added cost of making local calls from the telephones "an extreme charge."

Installing coinless public phones, he contended, could lead people to believe they don't have to pay more than the regular coin phone charges. He said local call fees should be listed on coinless instruments to avoid confusion and to make people "aware of the fact that they're paying a premium for convenience."

The telephone company has not listed the local call fees on the coinless instruments installed so far in the Washington area.

The area's first such phone was installed earlier this month at a Holiday Inn near Baltimore. Maryland is scheduled to have 50 of the telephones by the end of the year.

The District and Virginia will get coinless public phones within the next four months, although the number and locations have not been announced.

C&P spokesman Wann said long-distance charges for calls from the new telephones will cost the same as from any other telephone, and that the 40-cent and 50-cent charges for local calls are the same charged for local calls made with operator assistance.

Cuffe of the consumer affairs office, queried by a reporter about the new type of phone, said callers normally wouldn't make an operator-assisted local call from a coin phone. But that is the only way a local call can be made from the coinless variety.

The coinless public phones are cheaper to buy and operate than the coin-operated variety, and the Bell System market research division originally hit on them as a way to reduce capital expenditures.

But savings "don't mean we have to roll back charges for customers -- it just means we don't ask for a rate increase as quickly," Wann said.

Coinless telephones were introduced two years ago at LaGuardia and Kennedy airports in New York. Wann said that eventually 10 percent of C&P's public phones will be of the coinless variety.

The telephone company has pinned its hope for the new phones' success on customer snobbishness.

"There is some status attached to walking up to one of these modern telephones," which are blue, ochre and white and have a futuristic shape, said Wann, "and making a call" while the ordinary caller drops coins into one of the run-of-the-mill black-and-chrome square models.