A widespread outage at Verizon affected cellphone customers in California and the U.S. on Monday, limiting some residents to emergency calls called SOS mode.

Downdetector, a website that collects reports of such disruptions, showed that hundreds of customers in the Sacramento area began reporting power outages around 7 a.m.

The New York-based telecommunications company acknowledged the problem and said its engineers were trying to identify and resolve it. AT&T suffered a similar outage in February, when tens of thousands of customers temporarily lost service.

Verizon, the largest wireless carrier in the US, has 114.2 million retail wireless customers. According to the company, revenues exceeded $24 billion in the second quarter of 2024.

SOS mode is a relapse

According to Apple, SOS mode is a fail-safe for iPhones and other smartphone devices when cell phone networks are unavailable.

The phones automatically switch to SOS when the connection fails, but allow cellphones to make emergency calls, such as 911, by using other wireless carriers’ networks.

Some customers took to social media to express their frustration over the outage as it prevented them from using two-factor authentication. This security measure typically involves sending a verification code to a user’s mobile phone when logging into a website.

As a result, these users are unable to access their accounts, including essential services such as banking and work emails, as well as their Verizon accounts.

“Also, how can I log into my Verizon account if I can’t verify who I am by receiving a text message due to an outage?” one user wrote on X.