The problem started at around 3 p.m. Saturday. Sunday, AT&T officials said in a statement that most areas have been restored to normal operation, but few areas remain affected. The statement did not specify which areas were still having problems.
AT&T said the issue stems from a hardware issue that has affected hundreds of towers and thousands of customers.
Most users have been able to send and receive text messages and use the Internet. The making or receiving phone calls is what's been tough.
AT&T offered its customers an apology for the outage.
The Associated Press contributed to this report.