As Pentagon spending goes, $25,000 could be considered pin money - loose change in the Defense Department's pocket. But when the Pentagon inspector general recently reported that one department's bills to a New York ''dial-a-porn'' telephone sex service were running as high as $25,000 a month, the sum no longer seemed much like petty cash.
There is something particularly nasty about members of the department that most aggressively claims the taxpayer's money misappropriating it on a dirty snicker. But even more disturbing is the awareness the incident forces upon us of a new gross abuse of the telephone. These things happen in stages. We have become accustomed - perhaps too accustomed - to the retailing of the commodity of pornography in an adult bookstore or a movie theater or even on cable TV. But now our favorite public utility - the social instrument that advises us to ''reach out and touch someone'' - is being perverted to antisocial uses with a blandness and a businesslike respectability we ought to find more alarming than we seem to.
Two types of services are booming. One - the kind involved in the Pentagon case - features recordings by women supposedly pictured in a pornographic magazine. Calls are free except for message units or long-distance charges.
The other services, operating under names such as ''Naughty Lady'' and ''Fantasia Mistress'' and advertised in publications such as the Village Voice and the Boston Phoenix, involve live conversations between women and paying customers. Costs typically range from $30 to $40 (''major credit cards accepted'').
Either way, phone companies profit. Ma Bell, it may not be too much to say, has become a madam through this verbal prostitution that gives new meaning to the phrase ''call girl.''
The other accomplices, of course, are credit card companies. Without plastic money, these services would find it far more difficult to operate and flourish.
It is a federal crime for an adult to place a $2 bet on a horse race over the telephone, but a child can ''dial-a-porn'' with the freedom of access equal to that of a Pentagon officer. One mother of four in North Andover, Mass., a PTA president, found 27 calls to a New York call-in sex line on her home telephone bill in October, placed by her fourth- and fifth-grade children. She is now organizing a letter-writing campaign to the federal government.
''I believe everybody has a right to freedom of speech,'' she has said, ''but when children are the consumers of it there has to be some way to limit access.''
Legislation signed into law last month makes any commercial telephone service using ''obscene or indecent'' language illegal if it is available to people under 18 years of age. In an effort to find ways to enforce the law, the Federal Communications Commission invited public comment. Early suggestions included limiting the services to late-evening hours when parents are presumably home, and using an automatic screening device, such as a user access code.
Although these tighter regulations would help, they fail to address the larger, more troubling issue. Anyone who has ever received an obscene phone call knows the shock, the sense of violation, such a call can produce. It is, in fact , an offense punishable by federal criminal penalties. But do these ''dial-a-porn'' services subtly blur the distinction between legal fantasy-sex calls and illegal obscene calls, making the latter easier or more tempting by establishing the telephone as an acceptable medium for sex?
We recognize physical brutality - the abuse a camera can register. But mental assault, where it all starts, is harder to identify. When there aren't any recognizable consequences immediately, everyone goes soft - disclaiming responsibility for crimes not proved. The phone company says, in effect, that its job is to make electronic connections between parties desiring or paying for such a connection, while the computers of the credit-card companies accept plastic sex along with plastic everything else.
There are First Amendment considerations to be scrupulous about. But should they be allowed to paralyze us?
There is a point at which the rights of the consumers of pornography begin to impinge on the rights of the rest of us, like cigar smoke drifting into the nonsmoking section. We should ask ourselves if the telephone does not constitute a private space that should not be easily invaded. The corruption of the telephone does not constitute the corruption of a mere ''entertainment medium,'' but of the intimate communication line that binds loved one to loved one, friend to friend. The realization of this ought to keep us properly uneasy until a responsible resolution can be worked out.