If you haven't reviewed your long-distance calling plan in the past couple of years, you're probably paying more than you have to.

So much has changed in just the past year in the Hawaii-mainland calling market that a reassessment of your long-distance service may be worth your while.

At the very least, you now have more choices.

Several companies, including GTE Long Distance and Nynex Long Distance, have entered the market in recent months, trying to lure customers from Hawaii's two main carriers, AT&T and Sprint.

At least seven companies currently are battling for a share of the state's $200 million-plus market, touting simplified calling plans and low rates.

But if consumers don't stay on top of the changes, they often can't take advantage of the benefits, experts say.

"Things are changing faster than they ever have before," said Boyd Peterson, a telecommunications analyst with the Yankee Group in Boston.

"Even a year and a half is a long time in long-distance years," agreed Aaron Golub of Telecommunications Research & Action Center, a nonprofit Washington, D.C, organization that tracks long-distance rates.

If a consumer hasn't reviewed his or her calling plan in the past few years, "it's absolutely worthwhile to do it," Peterson said.

If you ask, the phone companies will even do it for you.

Tell them how often you make long-distance calls, where and when you call and how much you generally spend each month, and they will recommend the best calling plan for your profile. Once you get recommendations from several companies, you can decide which carrier to pick.

Comparing has become easier since companies starting offering flat-rate plans. Carriers have simplified their offerings to counter widespread consumer confusion over volume-discount plans and other complicated hybrids.

In many cases, customers can get a single rate no matter what time of day they call, where in the United States they call or on what day. Other plans have two rates: day and evening/weekend.

For Hawaii, the trend is good news. Customers on such plans no longer are charged based on which region of the United States they call -- a typical characteristic of variable-rate plans.

"Flat rates are a good deal for Hawaii," Golub said.

"They give a lot of people peace of mind," knowing exactly how much they'll be charged when they place a call.

But he cautioned to make sure that the plan they pick best fits their calling patterns. If someone makes most of their long-distance calls in the evenings and on weekends, a single-rate plan might not be the best, he said.

Plans offering two rates -- with the evening/weekend price cheaper than the single rate -- might be a better choice.

The problem many consumers have, Golub said, is they're not on any kind of discount plan.

Almost two thirds of Americans are paying basic rates, the highest offered by carriers, according to a Yankee Group survey.

Those customers probably can save 35 percent to 54 percent from their long-distance bills if they switch to a discount plan, even if they remain with the same carrier, Golub said.

If you aren't on a plan, the only way to sign up is to call the carrier directly. The companies usually have toll-free numbers.

If you switch carriers, your new company typically will offer to pay the switching fee (just over $4) imposed by GTE Hawaiian Tel, but be sure to ask about that.

The single-rate plans generally benefit people who make a lot of long-distance calls during the day, analysts say.

Golub's organization just released a survey that shows the Big Three -- AT&T, MCI and Sprint -- are offering some of their most competitive deals ever to consumers with the biggest long-distance bills.

But even moderate users are benefiting from the competition, Golub said.

In Hawaii, the biggest benefit has been in the interisland market, where toll charges have dropped substantially since the market was opened to full competition last year.