Wednesday, the Dallas-based carrier suspended its preorder program for Apple Inc.'s new phone.
The suspension came a day after unprecedented demand for the new iPhone crashed AT&T's website and led to many customers reporting a variety of errors, including one glitch through which some customers accidentally logged into other AT&T customers' accounts.
The struggles ahead of the release of the iPhone 4 next Thursday were a surprise, given this is the fourth year in a row AT&T has had to manage the excitement around a new iPhone.
But AT&T and Apple said Monday's preorder mania was unlike anything they've seen before.
Apple said 600,000 preorders for the iPhone 4 were placed Tuesday.
"It was the largest number of preorders Apple has ever taken in a single day and was far higher than we anticipated, resulting in many order and approval system malfunctions," the company said in a prepared statement.
"We apologize to everyone who encountered difficulties and hope that they will try again or visit an Apple or carrier store once the iPhone 4 is in stock."
The new iPhone has a higher-resolution screen than those on previous models, can shoot and edit high-definition video, and make video calls over Wi-Fi. The model with 16 gigabytes of memory costs $199, with a two-year AT&T contract, while the 32-gig version costs $299.
AT&T said it halted the preorder campaign because it sold out of its initial allotment of phones.
"iPhone 4 preorder sales [Tuesday] were 10 times higher than the first day of preordering for the iPhone 3G S last year," AT&T said.
"In addition to unprecedented preorder sales [Tuesday], there were more than 13 million visits to AT&T's website, where customers can check to see if they are eligible to upgrade to a new phone; that number is about three times higher than the previous record for eligibility upgrade checks in one day."
AT&T was less forthcoming, though, about a host of technical glitches and possible security holes reported by buyers on various technology blogs and websites.
Some preorder hunters trying to log into their AT&T accounts on the website reported being accidentally logged into other users' accounts.
In some cases, the preorder shoppers saw credit card information of other users, claims that were backed up with screen shots posted on tech blog Gizmodo.
There were also complaints that shipping addresses were mixed up. Some people preordering online noted that their new purchases were set to be shipped to someone else.
Indeed, some AT&T subscribers who did not try to preorder the iPhone 4 reported getting iPhone preorder confirmation notes from AT&T.
AT&T downplayed all those reports and asserted that no credit card data was compromised.
The company also declined to make any executives available for interview, opting instead for prepared statements.
"We have received reports of customers inadvertently seeing the wrong account information during the iPhone 4 purchasing process," the company said.
"We have been unable to replicate the issue, but the information displayed did not include call detail records, Social Security numbers or credit card information. In the meantime, we are looking into this matter."
It's the second major customer data breach in as many weeks for AT&T.
Last week, a team of hackers uncovered a flaw in AT&T's website that produced the e-mail addresses of owners of the Apple iPad with 3G wireless Internet access.
But one expert said the flurry of glitches and breaches shouldn't dampen sales of the new iPhone.
"We have seen this kind of goof happen from time to time with many companies," said telecom analyst Jeff Kagan. "It gets a lot of attention when it happens, then it usually gets forgotten about, unless this becomes an ongoing problem."
And, as Tuesday's preorder frenzy proved, the iPhone is simply irresistible to many people.
"The iPhone is not a normal phone," Kagan said. "Customers can complain, but they will not turn away from the iPhone."
An analyst with Piper Jaffray on Wednesday raised his sales estimates for the iPhone 4 by 1 million units, saying he now expects Apple to sell 9.5 million phones by the end of June.
