BRENTWOOD—An outage caused by a software glitch affected AT&T business customers on Monday, April 3 in cities such as Brentwood, Studio City, Pacific Palisades, and other areas throughout Los Angeles, City News Service reported.

Cedars Sinai-Medical Center in Los Angeles sent out an email to clients and staff informing them that they were not receiving calls from the outside because of the outage. At 9:40 a.m., the medical center announced via Twitter that it was “due to a national AT&T outage.”

At 3:33 p.m., the medical center tweeted: “All incoming and outgoing phone lines are working again at Cedars-Sinai. Thank you for your patience and flexibility!”

According to, service problems from AT&T were also reported by businesses in major cities such as Dallas, Houston, San Antonio, Mountain View, Austin, Miami, St. Louis, Chicago and New York.

“We apologize to our customers who were affected,” said AT&T in a statement related to the software issue that was affecting business for voice customers.