Michael J. Leake thought he had it wired when the Los Angeles entrepreneur acquired use of the phone number 1-800-366-4667.

He planned to use the toll-free number, which happens to spell DOMINOS, as part of an elaborate marketing strategy he devised that would make it easy for customers to contact Domino's Pizza, the world's largest pizza-delivery firm, with 4,800 outlets nationwide."I had the foresight to know that number would be valuable," he said, "and I got that number knowing Domino's would have to come to me."

But before Leake took his plan to Domino's, he charges, the long-distance company that leased him use of the phone number, US Sprint, took it away and gave it to Domino's Pizza. At the time, Leake says, Sprint claimed there was a prior reservation by another party - Domino's.

Now Leake's company, 5-year-old Dial 800 Inc., is suing both Sprint and Domino's, charging breach of contract, fraud, conspiracy and interference in an "advantageous economic relationship."

The lawsuit, filed last month in Los Angeles County Superior Court, names as defendants both Domino's Pizza of Ann Arbor, Mich., and US Sprint of Kansas City, Mo.

According to the lawsuit, Dial 800 signed a contract with Sprint in June 1987 for use of two toll-free telephone numbers. One of these was 366-4667. The two numbers were eventually installed at an automated answering service in January 1988, the suit maintains. They remained hooked up until June 13, when Sprint took back the 366-4667 number, citing the prior reservation by Domino's - a claim the lawsuit brands as false.

Representatives of both Sprint and Domino's declined comment on the lawsuit, which they said they had not yet seen. But Domino's spokesman Ronald Hinghst, said that the company uses the number now as a complaint line for customers.

Use of toll-free numbers has grown rapidly since their introduction in 1967. In 20 years, the number of 800 prefixes grew from 650 to 500,000 with 6.3 billion calls placed.

What he had in mind for Domino's, Leake explained, was a national toll-free telephone number that would allow customers anywhere to have their call forwarded directly to the company's nearest pizza outlet.