T-Mobile users reported a spike in service disruptions on Monday, according to outage tracking websites. 
Downdetector.com reported that outages peaked at around 81,000, up from a baseline of 46. Comments on the site show disruptions occurred in New York, Chicago, Seattle, Phoenix, Houston, Dallas, San Diego, Dallas, Los Angeles, and Las Vegas. 
"This is so annoying. Working, not working, on -off all night and still not fixed," user Jackie commented in the early morning on Tuesday. 
The company has not yet revealed the exact cause of the outage, but did say that issues originated from a third party. 
"Our teams are rapidly addressing a 3rd party fiber interruption issue that has intermittently impacted some voice, messaging and data services in several areas," T-Mobile President of Technology Neville Ray tweeted on Monday night. 
As of Tuesday morning, the company said the issue was mostly resolved. 
“We have seen significant improvement and are operating at near normal levels," Ray tweeted. “Our teams continue to monitor and we greatly appreciate everyone’s patience. We apologize for any impacts this issue may have had for our customers.”
Many customers are now asking for partial refunds on their bills, with some reporting that they were unable to make emergency calls. 
A similar issue previously brought regulatory troubles for T-Mobile in 2021, when the company paid $19.5 million to settle a probe into an outage that led to 20,000 failed 911 emergency calls.