In this Feb. 14, 2018, photo, the logo for T-Mobile appears on a screen at the Nasdaq MarketSite in New York. T-Mobile, one of the three largest mobile carriers in the U.S., said it's working to fix a widespread network issue. The company's president of technology, Neville Ray, tweeted Monday afternoon, June 15, 2020, at around 4 p.m. Eastern Daylight Time that T-Mobile engineers hope to fix the "voice and data issue" soon. (AP Photo/Richard Drew)

T-Mobile, one of the three largest mobile carriers in the U.S., said it's working to fix a widespread network issue.

The 's president of technology, Neville Ray, country's largest carriers, along with AT&T and Verizon, after buying rival Sprint. The company has started integrating the two networks.

The Federal Communications Commission, which oversees voice and data networks, said its public-safety bureau is looking into the problem.

T-Mobile paid a $17.5 million fine for two nationwide service outages on the same day in August 2014, which together lasted three hours and prevented customers from being able to call 911.