THE BREAKUP of the Bell System intruded upon dinner a few weeks ago.

"Would you like a free T-shirt?" the comely female asked diners at each table in the House dining hall.

All you had to do to get one was fill out a card with your name and phone number. The T-shirt you got explained what you had just done. It read "I FOUND MY CALLING with AT&T Long Distance Service."

As a result of a federal antitrust action in 1982, the monopoly American Telephone & Telegraph Co. enjoys over long distance service is being replaced by a policy the Federal Communications Commission calls "Equal Access." Under this policy, all long distance firms (MCI and Sprint are among the better known) will have access to the same equipment and services from independent local telephone operating companies (like New England Telephone). The consumer, in turn, will be able to choose which firm will carry his call after he picks up the receiver and dials "I". The policy is gradually being implemented across the country, until all consumers have had a chance to choose their long distance carrier. As Harvard diners recently found out, Equal Access has now reached Cambridge.

For months, AT&T has bombarded consumers with an advertising campaign designed to convince them to pick AT&T as their long distance phone carrier AT&T as their long distance phone carrier AT&T operators encourage callers to choose their company with each collect call they assist, while actor Cliff Robertson (who one AT&T executive described as "literally dripping with integrity") declares to TV viewers that "the more you hear, the better we sound."

Sprint, MCI, Allnet, and some of AT&T's other competitors also participate in the growing ad war, but none has rivaled Ma Bell's assault on collegiate conversationalists. College Students call home a lot, AT&T reasons, and the folks often foot the bill. As a result, the only advertisement as frequent as that for ROTC in collegiate publications is the AT&T Thinking Student.

Clad in gym shorts, he sits on a stack of textbooks, thoughtfully clenching a telephone receiver in his right hand. As he stares at the red pushbutton phone on the ground, he seems to ponder the wisdom of the advertising copy that surrounds him. "If you think about it, you'll choose AT&T," that copy concludes, But is that really so?

"THINK ABOUT AT&T'S SPECIAL CREDIT." Each month your AT&T still is more than $15, the company will give you what they call an "Opportunity Calling" credit. These may be applied to various specified brands of merchandise, for a discount. Every three months you receive a statement telling how many credits have been accumulated, and what they can be accumulated, and what they can be redeemed for.

Sally Lawrence, a spokesman for the Federal Communications Commission, told The Crimson she had looked at the Opportunity Calling catalog, and, in her opinion, "you would have to make an exhorbitant amount of calls for it to be of any use." AT&T's Terry Romano countered, saying that $5 credits for Levi's jeans were among the items of possible interest to students. However, Stan Sesser, west coast editor of Consumer Reports, called the service "a real hassle" and said it was pointless to "buy a more expensive telephone service in order to get a cheaper blender." With the number of calls her family made, Lawrence said "we maybe qualified for a clothesline."

"THINK ABOUT AT&T SERVICE." AT&T does have more operators than the other firms, which generally do not provide the operator service necessary for collect and person-to-person calls. Under the Equal Access regulations, however, it will be possible to reach AT&T (and all other carriers) by dialing a five-digit number even if you choose a rival firm as your primary (dial 1) carrier. Romano confirmed that which ever long distance company you choose, "there will always be an AT&T operator available" if you need to use one.

"THINK ABOUT AT&T'S QUALITY." AT&T says its "calls sound loud and clear-as close as next door." Sesser, however, reported that both his survey of long distance services and Consumers Checkbook, a Washington-based consumer group, found SBS Skyline to have the highest voice quality of all carriers. AT&T was second best. The ad says "only AT&T lets you call from anywhere to anywhere," but Sesser said that now virtually all long distance companies can reach all locations in the United States, and some reach an increasing number of foreign countries.

"THINK ABOUT AT&T'S DISCOUNTS." AT&T is the most expensive long distance carrier in the country. Lawrence explained that the FCC grants AT&T's competitors a 55 percent discount in local access fees to help compensate for AT&T's advantages as the former telephone monopoly. According to the March issue of Consumer Reports, the least expensive service was SBS Skyline, followed, in order of increasing rates, by Western Union, Allnet, ITT, MCI, GTE, Sprint, and AT&T, SBS Skyline, according to Sesser, was "the over-whelming choice. Not only was it the cheapest service, but it had better voice quality than AT&T."

"IF YOU THINK ABOUT IT, YOU'LL CHOOSE AT&T." Really? Since there is little factual reason for a consumer, especially a college student, to choose what is the most expensive telephone service. AT&T has run, a campaign based on repetition, rather than reasoning. Whether AT&T' dinner-table tactics are merely "aggressive," as Romano claims, or "bordering on predatory," in Lawrence's words, students should think carefully about then long distance, carrier and make a choice based on what saves them the most money.

Incidently, AT&T would be as happy with non-thinking students as with the tail Thinker pictured in its ad: customers who fail to indicate an alternate choice for long distance carrier will automatically remain with AT&T, and they won't even get T-shirts.