Verizon customers across the U.S. reported problems accessing the company's wireless network, with some reporting Monday morning that their phone service was down and limited to SOS mode. 

The service was fully restored by Monday evening, according to a Verizon spokesperson. 

Outages were reported from New York to Los Angeles, with the main complaint linked to lack of service on customers' mobile phones. Customers began reporting problems shortly after 9 a.m. ET on Monday, with some turning to social media to ask Verizon for refunds. 

As of 10:11 a.m. ET, more than 100,000 reports of Verizon outages had been logged with DownDetector, a site that tracks service outages for telecommunications providers, websites and other businesses. 

"It's been over two hours and we don't even know why this is happening. We all pay a pretty penny for our Verizon bill, this time should be compensated until the issue is fully resolved," one customer posted to Verizon's customer support account on X.

People across the country said their phones had no service except for SOS mode.

"SOS in Ohio since mid-morning. Was working on my drive into work, but went down several hours ago and hasn't come back," one user wrote on DownDetector. 

When is Verizon coming back up?

In an initial statement emailed to CBS MoneyWatch, Verizon said its engineers were "working quickly to identify and solve the issue." 

In a later update emailed to CBS at about 5 p.m. ET, Verizon said that service was beginning to be restored to customers. 

"Verizon engineers are making progress on our network issue, and service has started to be restored," the spokesperson said. "We know how much people rely on Verizon and apologize for any inconvenience some of our customers experienced today. We continue to work around the clock to fully resolve this issue."

What is SOS mode? 

Mobile phones will sometimes switch to SOS mode when they're having trouble connecting to a wireless network. As the name suggests, SOS mode means the phone can still make emergency calls, such as 911, by connecting to other carriers, according to Apple.

Some customers complained on social media that the outage is making it impossible for them to use 2-factor authentication, which is when a company sends a code via text to a customer's mobile phone during login as an added security precaution. The customer then uses the code to access an account, such as financial services account or work email — as well as their Verizon accounts.

"Also how can I log into my verizon account if I can't verify who I am by getting a text because of an outage?" one user wrote on X. 

The outage appears to be affecting both iPhone and Android users, according to tech site Bleeping Computer.

As of 4:30 p.m. ET, Verizon's post on X about the outage had drawn more than 7,000 responses, many from customers asking for updates and expressing anger about the disruption. Some noted they were unable to make business calls or reschedule appointments because of the service disruption, with many customers vowing to switch carriers. 

"As soon as this problem is fixed I'm canceling my service," one customer wrote in response to Verizon's X post. "Mostly because you have yet to say what the cause of this is … and it's not just 'some customers.' It's on a very wide scale."