(NEXSTAR) — If you're an AT&T customer, there's a good chance you haven't forgotten about the hours-long outage the company experienced last week.

On Thursday, thousands of AT&T users reported that they were unable to make calls or use their data. Outage tracker Downdetector noted that outages, which began at about 3:30 a.m. ET, peaked at around 73,000 reported incidents. AT&T had more than 58,000 outages around noon ET on Thursday, in locations including Houston, Atlanta and Chicago.

The carrier has more than 240 million subscribers, the country’s largest.

Some iPhone users saw SOS messages displayed in the status bar on their cellphones. The message indicates that the device is having trouble connecting to their cellular provider’s network, but it can make emergency calls through other carrier networks, according to Apple Support.

AT&T says outage not caused by cyberattack

By early evening Thursday, AT&T said it had restored wireless service to all of its affected customers.

Late Sunday evening, the company said it would be reimbursing those that were impacted.

"We apologize for Thursday’s network outage. We recognize the frustration this outage has caused and know we let many of our customers down," AT&T wrote on its website. "To help make it right, we’re reaching out to potentially impacted customers and we’re automatically applying a credit to their accounts. We want to reassure our customers of our commitment to reliably connect them – anytime and anywhere. We're crediting them for the average cost of a full day of service."

A note on the company's website said that reimbursement will be a $5 credit per account to your AT&T Wireless account. The offer does not apply to AT&T Business, AT&T Prepaid or Cricket. Users of Cricket, which is owned by AT&T, also experienced outages on Thursday.

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AT&T said Thursday that the outage was not caused by a cyberattack, based on an initial review, The Hill previously reported. Instead, the company said it believes the outage "was caused by the application & execution of an incorrect process used as we were expanding our network."

The Federal Communications Commission (FCC), Department of Homeland Security (DHS), and the FBI confirmed Thursday that they were investigating the outages. It's unclear if that is still the case.

In Saturday's statement, AT&T wrote it is "taking steps to prevent this from happening again in the future."

"Our priority is to continuously improve and be sure our customers stay connected."

The Associated Press contributed to this report.