The first time Natalie Jones, 17, worked the telephones, she made about 120 calls and got an earful of complaints.

"One man even told me he'd rather have the Devil in office than President Reagan," she says.

But Jones, a senior at Marshall High School near Falls Church, also got hooked, and she enlisted as a foot soldier in the telephone warfare that has become a key element in the fall elections in the Virginia suburbs. As she put it after a night of Cokes, pizza and telephone calls for the Republican Party: "It looks like this campaign is going to be really fun."

Callers such as Jones, deployed at 25 large telephone banks across Virginia, are one reason the GOP is expecting Republican candidates to do extremely well in the Nov. 6 elections. In slightly more than a decade of operation, the banks, which will cost the Virginia Republican Party $200,000 to operate this fall, have become an established way of campaigning for many politicians in the state.

Nowhere do they appear more important than in Northern Virginia, where politicians say the phone banks are one of the best links a candidate can have with an often transient constituency.

The Democratic telephone counterpunch this fall is more diffuse, coming from an estimated 200 phones scattered throughout the Washington suburbs and often working for an individual candidate rather than for the entire ticket.

Pat Watt, Fairfax County Democratic Party chairman, concedes the telephone battle to the GOP. "It's because they've got the big bucks," she said. "It costs a lot of money to put that many phones in one location."

"Part of that is because there's no presidential involvement in this state," grouses Joe Gleason, spokesman for Democratic State Sen. Richard L. Saslaw, who is challenging 8th District Rep. Stan Parris and is using 50 phones spread over a a dozen locations.

Democrat John P. Flannery, who is facing Republican Rep. Frank R. Wolf in the 10th District, has 51 phones in four locations, and his staff is more upbeat than Saslaw's staff about their impact. Flannery's wife and campaign manager, Bettina Gregory, said the phone banks have been "extremely successful," but she declined to say how many voters have been contacted.

Phone banks first made the difference in Virginia in 1973, when Mills E. Godwin Jr. was elected governor a second time by only 15,000 votes, said J. Kenneth Klinge Sr., a prominent GOP strategist and director of special projects for the Reagan-Bush campaign.

They provided Republican Sen. John S. Warner with the narrow margin of his 1978 victory of 4,751 votes, and, three years later, they helped Democrat Charles S. Robb win the governorship by 100,959 votes, making him the first member of his party to exploit the telephone banks on a statewide scale.

Big or small, phone banks usually operate the same way. Campaign workers read from a prepared script, calling specified precincts, or groups of people, such as federal employes.

To Klinge, paid callers are the best. They typically make about 25 calls an hour, while volunteers average 15. And, he says, on a given day, 80 percent of the paid help will show up, but only half the volunteers.

Despite this, Klinge prefers volunteers "if I can work it," because of their esprit de corps.

At 6 p.m. on a recent Thursday, the 10th District Republican phone bank in Merrifield was crowded with high school volunteers, many of whom had come to fulfill government class requirements that they give 10 hours of time to the campaign of their choice.

The volunteers were served pizza, Coke and chocolate chip cookies, along with a healthy dosage of conservative politics.

For the next three hours, the students worked from their scripts ("Hello. I'm -----, calling from Merrifield, and I'm doing a survey"), calling about 500 households on behalf of Reagan, Warner and Wolf.

Undecided voters are sent mailings and then called later to see whether they have switched. All favorable voters were earmarked for subsequent get-out-the-vote calls on election day.

In all, since Labor Day, 10th District volunteers have phoned 20,000 persons, and supervisor Mary Williams said she hopes to contact two-thirds of her district by election day, Nov. 6.

"I think it's pretty much fun," said Tony Perez, 18, a senior at Madison High School. "Everybody here is like really relaxed. They just call the people and hope they get a nice person on the line."

Michael May, 17, a senior at Marshall High School, said most of his calls went to Republicans. "But a couple of people have given reactions like: 'Don't you know we're in the middle of dinner?' Or, 'Don't you know we're on our way to a soccer game?' "

There are some signs that the Republican phone banks may have lost some of the edge they once enjoyed. "Back in the years when we did it and the Democrats didn't, it was extremely effective," said Donald W. Huffman, state Republican chairman. "Now, both sides are doing it, and it becomes kind of a wash."

Some even wonder if phone banks eventually might be replaced by direct mail -- the theory being that mail is less obtrusive.

George Stoddart, press secretary for Robb, disagrees. "I lead a fairly sedentary life style, and I'm home many nights, and I've so far received only one phone call from a polling bank so far this season. I didn't find it annoying."