The telephone rang. On the line was the traveling publicist for the Women's Tennis Association. She was passing through Washington on her was to New York for the $300,000 Avon Championships, which begin today at Madison Square Garden.Her sales pitch for the tournament would have sounded more authentic if she had rung the doorbell instead of phoning. You know: "Ding-dong, Avon calling."

The marketing strategy for this year's Avon Championships, the climactic playoff for the top eight point-winners on the women's winter pro tour, is evident. The Billie Jean King-Virginia Wade "old lady" look is out. The "whiz kid" look is in. The new face of women's tennis is, quite simply, new faces.

For every familiar figure -- two-time Wimbledon champion Martina Navratilova and teen-age overachievers Andrea Jaeger, Hana Mandlikova and Pam Shriver -- there is a relative stranger in the field.

Sylvia Hanika. Barbara Potter. Bettina Bunge. Leslie Allen.

Who are these persons?

The finished among the top performers on the 10-city, $1.55 million series of Avon Championship tournaments that began in January in Kansas City and concluded last week in Boston. Hanika won in Seattle, Allen in Detroit. Potter was runner-up in Seattle and reached the semifinals in Kansas City, Chicago and Detroit. Bunge was runner-up in Houston and a semifinalist in Seattle, Los Angeles and Boston. They all earned their places at the Garden.

"Of the eight players in the Avon finals last year, Navratilova is the only returnee. The other seven are in it for the first time," said Ana Leaird, public relations director of the Women's Tennis Association. "Martina is also the oldest player in the field at 24. Last year, King was 36 and Wade was 35. There are four teen-agers, Jaeger the youngest ever at 15. This just proves what we've been saying, that there really is depth in women's tennis."

Yes and no.

To be honest, two of the Avon eight would have been out in the cold if the best two American players, Chris Evert Lloyd and Tracy Austin, had played the winter tour.

Evert, 26, took a nine-week sabbatical to be with her husband, and returned only last week, winning in Boston. Austin, 18, the undefending champion (she beat Navratilova in last year's final), missed the entire tour with an ailing sciatic nerve.

Moreover, it is extremely doubtful that Hanika, Potter, Bunge, Allen or even 1978 U.S. Open runner-up Shriver is ready to mount a serious challenge for the $100,000 top prize at the Garden party.

The smart money is on Navratilova to recapture the title she won in 1979, over either Jaeger or Mandlikova in the final. Navratilova loves playing indoors on fast carpet, and appears to be approaching the form that made her the No. 1 woman player in the world in '79.She won four of the six Avon tournaments she entered, 24 of 26 matches, losing only to Jaeger in the final at Kansas City and to 18-year-old Claudia Kohde at Oakland.

What Hanika, Potter, Bunge and Allen represent is a vibrant new middle class in women's tennis. They are social climbers, talented and eager enough to make the early rounds of tournaments for more interesting than they used to be, capable of troubling the ruling elite regularly, pushing them to the edge of the ledge occasionally, and shoving them over now and then. t

They aren't going to win major titles at this point, but they have moved out the klingering old guard: the Wades and Kings, the Betty Stoves and Wendy Turnbulls and Rosie Casals. Along with such gifted prodigies as Jaeger and Mandlikova, they have given women's tennis an appealing new look.

As individuals and as a group, they are interesting, cosmopolitan, engaging. Consider:

Hanika, 21, is a left-hander from Munich who typifies the bonhomie of Bavaria. In addition to tennis, she has competed in skiing, auto rallies and soccer. In 1979, she beat Evonne Goolagong Cawley enroute to the final of the Italian Open, climbed from No. 35 to No. 16 in the computer world rankings and was voted the most improved player of the year by her colleagues. Injuries showed her progress in 1980, but this year she already has won at Seattle, was runner-up in Cincinnati, a semifinalist in Boston.

Potter, 20, a Connecticut Yankee was accepted at Princeton but put off the Ivy League in order to play the pro tour full time. Her father is an artist (mainly oils and water colors), her grandfather was a Pultizer Prize-winning foreign correspondent and military editor of The New York Times. Her best weapon is a left-handed serve of menacing pace and spin, the foundation of a formidable attacking game.

Bunge, 17, was born in Switzerland, grew up in Peru, lives in Florida, is a West German citizen and travels on a U.S. passport. If that sounds fishy, it is because her German-born father is a fish-meal broker with farflung international business interests. She completed an accelerated academic program to earn her diploma from Deerborne High School in Carol Gables, Fla., is fluent in German, Spanish and English and is tackling French. A delightful dynamo, she somehow found time to earn high rankings in both the U.S. and West Germany.

Allen 24, won her first pro event at Detroit in February and became the first black woman to win a significant tennis title since Althea Gibson was the national champion in 1958. The daughter of Broadway actress Sarah Allen, she was graduated magna cum laude from Southern Cal in 1977 with a major in speech communication. Once offered a track scholarship at Texas Southern, she was sponsored briefly on the tennis tour by comedian Bill Cosby.

Today's pairings in the opening session of the hybrid round-robin format that will qualify four players for Saturday's semifinals are Navratilova against Shriver, Allen against Mandlikova, Hanika against Potter and Bunge against Jaeger. An unexpected but not unattractive lineup. Thus, the "Ding-dong, newcomers calling" campaign. Will it sell? Your Avon lady hopes so.