How to decide which company rings true for you

How can a consumer tell if one long-distance company is better than another? asks Samuel Simon, author of the book ''Reverse the Charges, How to Save Money on Your Phone Bill.''

Even AT&T admits it would be difficult to determine cost savings of its new, proposed service called ''Reach out, America.'' (The service would charge $10 a month for an hour's worth of calls made on week-nights and weekends.)

Mr. Simon says ''there is no quick way'' for consumers to explore all the long-distance options. It takes real shopping. Mr. Simon's consumer research group, the Telecommunications Research and Action Center, in Washington, D.C., will soon be offering a pamphlet on the subject. He is also hoping to update his book by the fall.

Another place to look for information is Consumers' Checkbook, also in Washington. The group recently completed a study on long-distance billing practices and is coming out with a book, ''The Complete Guide to Lower Phone Costs,'' in June. Later this year, it expects to run a computer program that will analyze consumer phone bills to help people select phone companies. Bruce Lupin, who runs Independent Telecommunications Corporation, Bethesda, Md., also expects to add residential clients to his long-distance analysis business, probably in the fall.