Many customer complaints on social media focused on problems among its iPhone users.
According to the site, San Francisco, Los Angeles, and NY are among the cities being affected the most by the outage.
Customers say they're unable to make or receive calls and are immediately disconnected when trying to make a call. Some customers had better luck turning on Airplane Mode on their phones, then turning that feature off again.
Charles Manson Hospitalized ... 'It's Just a Matter of Time'
The 83-year-old was previously hospitalized in January for a severe intestinal lesion that required surgery to fix . In all, he and his followers killed nine people at four locations in July and August 1969, USA Today noted .
St. Louis, Dallas, Chicago and Atlanta are among the other cities affected.
AT&T is aware of the issue and said users should restart their devices. In the Bay Area Redwood City activated their emergency operations center in response to the outage saying it was a result of a "software update to the system".
It appears that customers using AT&T for phone and internet are experiencing outages across the United States.