First presidential debate to be held Thursday at 9 p.m.

AT&T, T-Mobile and Verizon, the three major cellular carriers in the U.S., on Thursday said a roaming outage is affecting customers traveling internationally.

The outage means that some customers who are abroad are currently unlikely to be able to make phone calls, send text messages or use cellular data. 

T-Mobile told CBS MoneyWatch that the carrier is "one of several providers impacted by a third-party vendor's issue that is intermittently affecting some international roaming service." The company added that it is working with the vendor to resolve the outage and restore service for customers.  

AT&T said that its mobile customers abroad were also affected. 

"The AT&T network is operating normally. Some customers traveling internationally may be experiencing service disruptions due to an issue outside the AT&T network. We're working with one of our roaming connectivity providers to resolve the issue," a spokesperson said in a statement to CBS MoneyWatch.

Verizon said that about 30% of its customers weren't able to make calls and that it's working to restore service.

The outage stems from connectivity issues at Syniverse, the third-party provider that handles international roaming services for all three carriers, according to CNN, which cited a statement from Syniverse. The disruptions began Thursday morning, according to the report.

"Since the onset of these issues, Syniverse has been working closely with our network partners to restore full service," the company said in a statement obtained by CNN. "We understand the inconvenience this has caused and appreciate your patience as we navigate this challenge." 

A Verizon customer visiting Italy confirmed to CBS MoneyWatch that they had no service as of Thursday afternoon. 

Some customers griped about the outage on social media, calling on their carriers to restore service for them while away from their home countries. They reported not being able to call Ubers and resorting to hitchhiking to reach their destinations, among other inconveniences. Some said they were unable to get in touch with family members abroad, calling the situation "dangerous."

"Every American traveling in Europe right now with Verizon is waking up unable to order an Uber, check banking, log in to their bank, use Google Maps, call a friend or hotel — anything — massive global roaming outage. Dangerous. Zero comms from Verizon. HELP," user Nick Ponton posted on social media platform X.

Actor Patrick Schwarzenegger was also among the Verizon customers affected by the international outage. 

"Does anyone else have Verizon and overseas?? Everyone I'm with phone just fully stopped working...anyone else??" he wrote on X.

Megan Cerullo

Megan Cerullo is a New York-based reporter for CBS MoneyWatch covering small business, workplace, health care, consumer spending and personal finance topics. She regularly appears on CBS News 24/7 to discuss her reporting.