The best news so far in the fight against so-called dial-a-porn came this past week from American Telephone & Telegraph. The long-distance telephone company took the profit out of commercial smutty phone calls.

With the money gone, the dealers in long-distance dial-a-porn may have been dealt a crippling blow.Affected by the AT&T action are the 900-numbers, usually advertised in various "adult" magazines. No 900-numbers have been available in Utah. The AT&T action does not affect the 976-numbers provided through local phone systems at so much per minute.

Under previous arrangements, AT&T had paid message providers two to five cents for every call over 2,000 per day. Since some services logged as many as 100,000 calls a day, they could earn $5,000 or more a day.

AT&T's action allows long-distance dial-a-porn services to continue to operate, but gives them no way to collect any money.

USWest, which includes Utah's Mountain Bell, says its policy is to prevent children from having access to "inappropriate material." Dial-a-porn has not been available under 900-numbers or 976-numbers.

The 976-numbers in Utah include teen group talk, various dating ser- vices, and other special messages. They have drawn public ire, however, mostly because of youngsters running up expensive phone bills while taking part in lengthy group calls at a so-much-per-minute toll.

Mountain Bell has offered customers a service that blocks access to 976-numbers at no charge.

While Mountain Bell has kept away from dial-a-porn, some phone sys- tems in other states have seen the 976-numbers used for dial-a-porn. California is a major example. But the communications industry is mounting a long-overdue counter-attack there as well.

California's Public Utilities Commission ruled this past week that telephone companies can take legal action against dial-a-pornography services in order to protect their business reputations.

The PUC ruled that public phone companies can act as private firms in determining the content of the 976 phone services.

Although the PUC ruling by itself doesn't automatically put the dial-a-porn companies out of business, Pacific Bell, California's largest phone company, has filed suit seeking to block its lines to a dozen pornographers.

Pacific Bell executives are optimistic about their case because of a deci- sion last year by a federal court of appeals in Arizona that upheld the right of Mountain Bell to disconnect dial-a-porn services.

In addition, Congress appears ready to get into the act. In a measure being readied for post-Easter consideration, phone company customers would have to pre-subscribe to specialized lines. All others would be automatically blocked.

This puts the responsibility in the right place, instead of forcing innocent customers to take the initiative to have their phone lines blocked.

For too long, the nation's pornographers have used telephones lines and publicly-regulated telephone companies to spread their profitable smut. That sordid business may be coming to a well-deserved end. The sooner the better.