Each time they check the mail, about 7,000 people in the mid-Atlantic states may be wondering if they made "The Right Choice" in signing up with American Telephone & Telegraph Co. for long distance credit cards.

A runaway computer at AT&T last month sent out, under separate cover, 10 extra copies of each card that the 7,000 customers had ordered. People who ordered one card were sent 11. People who ordered two were mailed 22.

Altogether, nearly 100,000 unwanted cards were diligently ordered up by the machine and are wending their way through the postal system, showing up in waves in mailboxes at homes and offices.

"They have just been coming religiously, every single day," said Pat Scanlon, a telecommunications engineer who lives in Alexandria. "I can count on them." He has accumulated 14 so far.

On Tuesday, an embarrassed AT&T mailed a letter of apology to the affected customers, suggesting that they destroy the extra cards.

The company said it would issue new cards with new numbers to customers who worried that the numbers on the extra cards had been compromised and might be fraudulently misused.

Ann Grossman, AT&T's card product manager, said that the error originated at AT&T's credit card center in Piscataway, N.J.

The company had been receiving complaints off and on from customers living in the area covered by Bell Atlantic Corp. -- Maryland, the District of Columbia, Virginia, West Virginia, Pennsylvania, New Jersey and Delaware -- that they had signed up for cards between May and August last year but had never received them.

To find out if there were more such people, AT&T technicians searched the card division's computer files, and came up with a list of about 7,000 names and addresses.

The list was "run" on an AT&T computer one day in late December to produce electronic orders for the cards. The list should have then been taken out of the computer.

The list, however, was accidentally left in and continued to run for 10 more days, generating orders for about 10,000 unneeded cards daily.

"We ended up with those people who waited a while to get their cards then getting their card order times 11," Grossman said. "It was more than an embarrassment. We hate to do anything that increases customer dissatisfaction."