The company says that it has since made "significant changes and improvements" to its services to ensure a similar outage doesn't happen again.
The fourth-largest carrier in the US has been hit with a fine over emergency services outages that affected its network last year.
T-Mobile has agreed to settle a complaint from the Federal Communications Commission over two 911 service outages in August, the government agency announced Friday. T-Mobile will pay $17.5 million to settle the case and be required to implement a "compliance program" that will limit the company's chances of suffering a similar outage in the future.
According to the FCC, T-Mobile suffered two outages to its emergency 911 services on August 8, totaling approximately three hours of downtime. During those periods, T-Mobile customers trying to place calls from their mobile devices to 911 emergency first-responders were unable to, according to the FCC. The government agency also charged T-Mobile with being too slow to alert first-responders to the outages and didn't have "appropriate safeguards" in place.
"The Commission has no higher priority than ensuring the reliability and resilience of our nation's communications networks so that consumers can reach public safety in their time of need," FCC Chairman Tom Wheeler said in a statement. "Communications providers that do not take necessary steps to ensure that Americans can call 911 will be held to account."
The impact, the FCC charged, could have been major. The agency said that, on average, 27,400 calls are placed to 911 from all wireless providers each hour. The T-Mobile outage affected nearly all of its nationwide customers.
"The safety of our customers is extremely important and we take the responsibility to provide reliable 911 service very seriously," a T-Mobile spokeswoman said. "We have made significant changes and improvements across a number of our systems since last year, and we will continue working to improve these critical systems with our partners to provide the standard of service our customers rightly expect from T-Mobile."