A local consumer group has issued a report on telephone costs asserting that "lesser-known long-distance carriers often cost callers less (and sometimes provide better service) than GTE Sprint, MCI and AT&T."

In addition to analyzing long-distance charges, the latest issue of the Washington Consumers' Checkbook magazine surveys local phone service costs -- including installation and repair -- as well as compares costs of leasing versus purchasing telephones.

The 64-page report does not recommend any one specific long-distance carrier as the best or least expensive but offers instead a series of "usage profiles" that consumers could use as a guide to selecting which service is the most cost-effective for them.

"We started doing the report more than a year ago," said Robert Krughoff, president of Washington Consumer Checkbook. "We knew that there would be a lot of changes and confusion as a result of the breakup of the Bell System . People can't figure out all the right answers by themselves."

The issue details 19 different long-distance plans for 72 hypothetical callers, each with a different usage profile. None of the plans, according to the report, wins consistently.

However, says Krughoff, "I think it's hard to think of a case where someone could not cut his long-distance phone charges by switching to some other alternate long-distance carrier."

For example, a relatively small consumer of long-distance services who makes brief long-distance calls and had a $10 bill from AT&T Communications would probably have had to pay $9.38 using GTE Sprint; $7.75 for Telesaver and $7.53 for U.S. Tel's HomeLine service.

A heavy long-distance user with $100 in long-distance charges would have had to pay only $83.48 for Satellite Business System's Skyline service for comparable calls or $81.34 for Telesaver.

The Checkbook report also attempted to compare the quality of the various services over a three-month span in the fall of 1983. Each of 710 calls was graded twice -- once by the caller and once by the recipient -- for such line-quality concerns as static, hissing and echoes.

The service winning the highest marks for quality was SBS's Skyline. Only 39 percent of its calls were considered "moderately" or "severely" defective by either the caller or the call recipient. AT&T was next on Checkbook's rating list with 45 percent, then GTE Sprint with 52 percent and Allnet with 62 percent.

At the other end of the ratings, Western Union's Metrofone service calls were heard as moderately or severely defective 74 percent of the time, with ITT having a 70 percent defect rating and MCI Communications Corp.'s long-distance service with 68 percent.

However, many of the cited carriers have made significant efforts to upgrade the quality of their long-distance communications in the last year. Moreover, the phasing in of "equal access" connections to the local phone companies should mean that there will be consistent-quality long-distance service, at least by 1987.

Recent rate requests by the local Bell operating companies before the various public utility commissions may "change the cut-off points for our local service guidelines" as to when a consumer may want to switch to another pricing option, says Krughoff, but he asserts that "the general advice will continue to apply."

For example, Checkbook suggests Maryland consumers consider switching from "flat rate" local service to economy service, where the consumer is charged on the basis of the number of calls made. A flat-rate customer who makes 90 calls a month could save roughly $60 a year by switching to the per-call option.

In addition to evaluating service costs and options, the report surveyed prices for more than 50 phones at 29 Washington area retailers. The survey indicated that catalogue showrooms typically have the lowest prices. Telephone stores and department stores charge the highest prices -- roughly 15 percent above catalogue-showroom prices. The report sells for $6.95 and is available from Checkbook, 806 15th St. NW, Suite 925, Washington, D.C. 20005.