Some of the top cellphone companies in the U.S. have reported outages as of Monday.
T-Mobile tweeted that its customers were experiencing service interruption and that the company was working to determine the problem.
Customers with AT&T, Verizon and Sprint also reported dealing with service outages.
Those wireless carriers pointed to T-Mobile as the cause of the problems their customers were experiencing.
Service tracking site, Down Detector, reported at its highest point that more than 100,000 customers reported outages in the U.S.
By Monday evening, the number had fallen to about 25,000.