UNITED STATES— Mobile carrier T-Mobile experienced a nationwide outage on Monday, June 15, specifically hitting Southern California the most.

T-Mobile, one of the three largest mobile carriers in the U.S., began experiencing issues with its data and voice, and the company’s president of technology stated,

“Our engineers are working to resolve a voice and data issue that has been affecting customers around the country,” tweeted Neville Ray, T-Mobile’s (TMUS) president of technology. The company later added that the outages are a result of a “widespread routing issue affecting voice & text.”

Many customers were left to use other communication apps, such as ‘WhatsApp’ and Facebook Messenger to communicate with loved ones as no calls could be made out or received on T-Mobile lines. This inconvenienced other mobile carrier customers when trying to get in touch with T-mobile customers.

On Monday afternoon there were more than 100,000 outage reports received from across the United States, which later dropped to one fourth of that original number as the mobile carrier continued to work on solving the issue.

Verizon and US Cellular customers were also affected, with outages also reported in Texas, Florida, New York, and Georgia. Some customers even claimed the outage affected their ability to call 911.