Leslie Pfenninger got a job yesterday. All it took was a call to President Carter over a national radio hookup, 2 1/2 weeks of publicity, and a Bureau of Alcohol, Tobacco and Firearms official who reads the news.

"Anybody who has guts enough to call the President, I want to hire," said Warren H. McConnell, bureau director of public affairs, who did just that and then put out a press release telling everyone the 21-year-old Pfenninger was no longer among the ranks of the unemployed.

"What I've learned from this is that you don't get discouraged, you just keep on trying," said the jubilant Pfenninger, who since her graduation in May, 1976, from Elizabethtown College had been pounding the federal pavements looking for a job as a statistician. She'll work as an assistant curator for the bureau's museum.

It all started March 5 when the frustrated Pfenninger, a Lanham resident, dialed a special number and joined upwards of nine million other Americans who were trying to talk to President Carter on the telephone during a nationally broadcast radio show.

Against all odds Pfenninger found herself among the 42 who did manage to speak to the President. Pfenninger boldly asked President Carter to lift restrictions on appointments to civil service positions so that young people like herself could find jobs in federal government.

The President was unable to promise anything along those lines, but in the wake of her telephone call Pfenninger became the subject of numerous new stories.

"Things just sort of took off," she said yesterday.

According to McConnell, he and bureau director Rex D. Davis decided to interview the spunky college graduate after reading about her still being unemployed earlier this week - without, they insisted, any White House pressure.

"No one asked us to give her a job," Davis said.

Her $9,300-a-year job as a GS-5 is as of now temporary, but after 4 1/2 months she will be able to seek a full-time bureau job, a spokesperson said yesterday.

Meanwhile yesterday, Pfenninger settled into her new job as assistant museum curator in the style to which she has become accustomed: posing for new photographers andgranting interviews.