(NEXSTAR) – Verizon, the country’s largest cellphone provider, apologized Wednesday night after issues lasting much of the day left subscribers suddenly left without service and stuck in “SOS” mode.

“If customers are still having an issue, we encourage them to restart their devices to reconnect to the network. We sincerely apologize for the disruption,” Verizon said in a social media post shortly after 10:30 p.m. ET.

Verizon also promised to provide account credits to affected customers, adding that “details will be shared directly with customers.”

Downdetector, a site that tracks outages, showed a large spike in issues affecting Verizon starting just before 12 p.m. Eastern Time.

Complaints started to pour in on X from people in dozens of states. Users reported their phones were in “SOS” mode, meaning they couldn’t connect to the network and make calls.

When a phone is in “SOS” mode, emergency calls to 911 should still work using other networks or a satellite connection.

The cell carrier’s support team responded to users less than an hour after the start of the issue, saying, “We are aware of an issue impacting wireless voice and data services for some customers. Our engineers are engaged and are working to identify and solve the issue quickly. We understand how important reliable connectivity is and apologize for the inconvenience.”

When customers continued to experience problems over eight hours later, Verizon pledged to work through the night to restore service, adding “Today, we let many of our customers down and for that, we are truly sorry.”

Some users reported service returned for some time, but then saw their phones went back to “SOS” mode in the late afternoon.

Nexstar reached out to Verizon for more information, but did not receive a response. The carrier had not identified the cause of the outage as of publishing time.