DownDetector.com, which monitors reports of outages in real time, showed customers complaining about a lack of service across the country including in Houston, New York and San Francisco.
AT&T has replied to several customers on the social media site, advising them to turn their phones off and then back on.
The company suggested users restart their phones to resolve the issue.
AT&T said Wednesday that some USA customers are experiencing trouble placing wireless calls but rebooting the device would fix the problem.
- AT&T customers reported issues making calls on Wednesday night.
Reuters reported that AT&T indicated it had no estimate when the problem would be resolved.
A nationwide AT&T outage prompted at least one Bay Area city to launch emergency measures to make sure that people could still make 911 calls.