IF YOU LIKE JUNK MAIL, you're going to love junk phone calls. They're the hottest new mass-marketing technique, according to a Newsday report.

You may wonder what's new about sales pitches coming over the phone. You may think you've already heard them all: the free trial offers for cosmetics, magazines, insurance and a hundred other things; the heart-tugging appeals from charities, the political spiels and the rest. But as Al Jolson said, "You ain't heard nothing yet." The next time a commercial call drags you away from dinner or out of the tub, the caller may not be a person at all. It may be a machine.

That's right. American ingenuity, in its relentless march, has come up with equipment that can automatically make phone calls, play a taped message and even record the consumer's response. The gear, Newsday reports, can place thousands of phone calls in an hour, at any hour of day or night - and can dial every conceivable number, including unlisted ones. So you will no longer have to go to the trouble of turning on the television or radio to hear your favorite celebrities plugging a favorite cause. They'll call you up instead, on tape.

But what if you think telephones were made for people, and have no desire to hear a commercial message smile? You have a problem. Phone calls come in the aural equivalent of plain brown wrappers: You don't know until you answer whether it's Aunt Minnie or a sales pitch on the line. And if you don't answer, Aunt Minnie may not call back later - but the automatic equipment probably will.

The only answer may be an answering machine. It also follows that the mass-marketeers will quickly find a way to program their machines to leave enticing messages in your machine to get you to call back. And so it goes. Eventually the regulatory agencies may makes some rules. Long before that, however, as the junk calls increase, a lot of harassed consumers may be tempted to turn off their phones entirely and shift their personal communications to another medium. One possibility is called the letter. It's much slower than a phone call, but it has one great advantage: You don't have to answer it at all.