After encouraging the public to buy SmarTrip cards by installing SmarTrip fare boxes on more than 1,000 buses, placing SmarTrip vending machines in 33 stations and requiring their use by anyone parking at a Metro lot, the transit system is running out of cards.

Metro officials said yesterday that they will stop selling the rechargeable, plastic fare cards Monday and will not resume sales until new supplies arrive in September. They had already ceased online sales Wednesday.

Transit officials said they were surprised by how many cards they have sold since June 28, when SmarTrip cards became the only way to pay for parking at Metro's many parking lots and garages.

"We weren't able to anticipate this," Metro Chief Executive Richard A. White told board members yesterday. "It turns out the crystal ball was cracked. It was foggy."

Those able to purchase the cards, which cost $5 each, have complained of poor customer service. Metro officials acknowledged that they have been overwhelmed by inquiries and need to hire more customer service agents.

Until SmarTrip card sales resume, anyone who parks at a Metro lot or garage and doesn't have a SmarTrip card must purchase a paper fare card at a station for the exact amount of the parking fee. That fare card must be handed to a parking attendant at the exit lanes.

Metro must hire 48 additional parking attendants to handle those transactions, at a cost of $34,000 a week, said Ray Stoner, who oversees Metro's parking program.

"I just think we're going to have an awfully hard time trying to explain this," said Gladys Mack, who represents the District on the Metro board. "This is a tremendous inconvenience for the customer."

Robert White, a spokesman for U.S. Rep. Thomas M. Davis III (R-Va.), chairman of the House Committee on Government Reform, said a congressional inquiry is likely. "Chairman Davis was disturbed to learn of Metro's lack of foresight involving the SmarTrip program, particularly because it means more than $30,000 per week will not be going toward things like fixing escalators, maintaining trains or otherwise making the subway system run smoother. The committee will certainly be seeking answers as to how this could have been allowed to occur."

When it introduced the SmarTrip card in 1999, Metro was the first transit system in the nation to offer a rechargeable electronic fare card that can be loaded with value up to $200. The transit system sees the SmarTrip card as the linchpin in its effort to end cash transactions in the system.

SmarTrip use steadily increased until late last month, when sales jumped. Not only were commuters who park at Metro stations buying the cards, but installing SmarTrip vending machines at the 33 stations also made it easy for other rail riders and for bus passengers to buy them, said Metro's Richard White.

"You've got this convergence of factors," he added. "We did so much broadcasting of SmarTrip cards that our other rail customers who never bothered to buy a card online or at Metro Center now all of a sudden, are using the new vending machines in the stations. And, all of a sudden [the SmarTrip fare boxes] are on the buses. There's just a lot of human nature going on here that we clearly were not able to anticipate."

Before June 28, Metro had sold about 8,000 cards a month. After that date, sales leapt to 4,000 a day. About 544,000 of the cards are in circulation. By late yesterday, the transit system had about 16,000 cards in its inventory.

Only one manufacturer, Cubic Transportation Systems Inc. of San Diego, can produce the SmarTrip card, and the process takes eight to 12 weeks. "These cards aren't sitting on an inventory shelf, waiting for us to buy them," said Greg Garback of Metro's finance department, who has been negotiating with the Los Angeles transit system to buy some of its excess electronic fare cards because they are manufactured by Cubic and would work in Metro.

Several Metro directors said they did not understand why the transit agency ordered too few cards. "Could we not have anticipated this?" asked D.C. Council member Jim Graham, who represents the District on the Metro board. "We've set this whole momentum into place, and then you're going to yank out the rug from under it."

Transit system officials who spoke on condition of anonymity said that at least one top manager had warned of a shortage months ago and urged the purchase of more cards but that her concerns were disputed by those who procure the cards.

Although SmarTrip cards are popular, some riders have run into glitches. And they say poor customer service has worsened their problems.

Jenifer Butensky, 30, was sold on the virtues of SmarTrip when she moved to the District in May. After a year in Dallas, where public transportation was dismal, Butensky was "thrilled" to be able to hop a bus from Georgetown to work at the U.S. Chamber of Commerce at 16th and H streets.

Until SmarTrip failed her a month ago, that is.

Butensky said she boarded a bus one afternoon, added $20 to her card and then tapped the card to the SmarTrip sensor, which subtracted her $1.25 fare. The next day, the sensor told her the card had no value when it should have registered $18.75.

To recoup her money, Butensky said, she has called Metro's SmarTrip customer service number 10 times. She has waited on hold for up to an hour, sent one e-mail and left one message. On the few occasions Butensky has reached a person, she has found little help.

"They kept telling me the system's down, so they have no record of my transaction," she said.

"I want my money back, but it's not even the money that matters. . . . It's when you talk to people on the phone constantly who just don't seem to care," Butensky added.

Alexandria resident Bob Koslosky, 50, tells a similar story. A month ago, he said, his SmarTrip card stopped working with $33 on it. "I thought it would be a relatively simple matter" to fix, he said.

He was wrong. Several phone calls and e-mails later, Koslosky still has not spoken to a SmarTrip representative. The customer service is "terrible, in all capital letters," said Koslosky, a federal worker. "I've never had such a problem."

One rider ordered a card online and received eight in the mail. It took him several calls to reach a customer service agent to cancel the extra cards. Metro officials said last night that they were unaware of any problems with online sales.

Ten agents at a call center in Reston handle complaints about SmarTrip cards. Four others answer e-mails and process damaged cards. With the surge in SmarTrip card sales, those workers are overwhelmed, said Murray Bond, director of SmarTrip operations for Metro. On Wednesday, the call center received 505 calls -- 200 more than on a typical day a few months ago, Bond said.

Often, the representatives are tied up talking to people whose problems they cannot handle, such as questions about SmarTrip vending machines or parking garages. Metro is adding two agents next week, Bond said.