Attention investors, business-people and professionals: Your telephone may ring one day this week, bringing an offer that's hard to refuse. "Sure-thing" contracts on spot crude oil. Buy now, sit back, and watch the price go up.

According to the New York State attorney general's office, credulous investors already have anted up about $45 million for these contracts -- money they're unlikely ever to see again.

The Commodity Futures Trading Commission, in conjunction with New York and 27 other states, is preparing a massive lawsuit against many crude-oil investment companies, alleging fraud.

Among the sales practices that make government officials dark under the eyes are: (1) Misrepresenting current price trends in the spot-oil market, which have been flat to down, rather than up; (2) holding out crazy promises of porfit; (3) misleading investors about the size of the sales fee; (4) sending progress reports that falsely imply you're making a profit; and (5) not really having any oil to sell.

New York state already has enjoined nine companies from doing business within the state. Three of the companies sued to overturn the order, but it was upheld.

The companies that, right now, should not be calling residents in New York state are the American Petroleum Exchange Corp., Bartex Petroleum Corp., Commercial Petrolera International S.A., Eastern States Petroleum Exchange, International Petroleum Exchange, Pan Eastern Petroleum Exchange, Ramco Petroleum, Universal Petroleum and the United States Petroleum Exhcange.

These companies were charged with selling unregistered securities as defined by New York law. Some are contesting the charge: The matter is now before the court.

Massachusetts has shut down Boston-based Ramco, charging that its sales practices violate the state consumer protection law. Also, the Massachusetts attorney general's office was unable to verify that Ramco did, in fact, have any crude oil to sell, or any true source of supply. A telephone call to company headquarters found Ramco's telephone disconnected.

Most of Ramco's customers bought contracts maturing in March. So they may not learn until then that their hopes have gone belly up. The attorney general's office says that a modest amount of money may be recovered from the company and distributed among its customers. If you bought a Ramco contract, make sure the Massachusetts attorney general knows who you are.

Several other states also have taken action against one or another company. But the fraud suit will move against any operators at once.

If you're doing business with any firm named in the government's suit, make yourself known to your state's attorney general. Officials don't expect to collect much money from any company shown to be acting illegally: Most of the funds apparently have been sent out of the country, where the feds can't get them. But whatever is seized may be distributed to customers and other creditors.

The curde-oil game works in a number of ways. One approach is to ask for $6,000 or $7,000 to buy a contract for 1,000 barrels of crude. The hapless investor thinks that he's making a downpayment on the oil. In fact, he has paid a nonrefundable sales fee. The spot price of oil would have to rise $6 to $7 a barrel just for him to get his sales fee back.

Reported oil prices have been rising so swiftly that $6 to $7 a barrel may sound like nothing. But salesmen encourage you to confuse the official, posted price for crude oil with the spot price charged on the open market. Official prices have leaped, but spot prices went nowhere for the past two months: In recent weeks, in fact, they've been heading down.

If you want to speculate in the price of oil, there's an easy way to do it legitimately. The New York Mercantile Exchange lists two futures contracts, one for No. 2 heating oil, one for No. 6 industrial fuel. These investments are avaiable through brokerage houses or commodities dealers.