A “nationwide issue” Tuesday that had been affecting calls between carriers has been resolved, AT&T said.

“The interoperability issue between carriers has been resolved. We collaborated with the other carrier to find a solution and appreciate our customers patience during this period,” the company said in a statement at around 7:45 p.m. Eastern Time.

Calls to 911 and between customers of the same carrier, like AT&T to AT&T, were not affected, AT&T said. Texts were not affected, and neither was the FirstNet wireless broadband network for first responders, it said.

Earlier the carrier said that it was working closely with Verizon to address the issue. The problem was not a nationwide outage, it said, but rather “a nationwide issue that is affecting the ability of some customers to complete calls between carriers,” AT&T said at the time.

Verizon had said its network was working normally, but “some customers, primarily in the Northeast and Midwest, are experiencing issues when calling or texting with customers served by another carrier.”

The Federal Communications Commission said it was looking into the matter.

“We’re aware of reports that consumers in multiple states are unable to make wireless calls and we are currently investigating,” the FCC said in a statement posted on X.

It was not clear how many customers were affected.

Some vented their frustration to support accounts on X. One directed a post toward Verizon, complaining “I pay too much to not be able to make a phone call.”

“What’s up with y’all today! My phone decided to stop making outgoing calls. Says it’s unable to connect,” another customer told AT&T on the social media platform.

The disruption occurred a little more than three months after a widespread outage affected AT&T customers, leaving people without service. During that incident, around 50,000 outrages were reported at one point. The company said then that problem was caused by a process error.

The website Downdetector noted a spike in reported outages for both AT&T and Verizon on Tuesday.

T-Mobile said it was not experiencing an outage, but the problems with other carriers might impact its customers trying to connect to other networks.

This article was originally published on NBCNews.com