The declaration follows recent news of an incident where Salt Typhoon, an infamous Chinese state-sponsored threat actor, breached T-Mobile's network in a cyber-espionage campaign on behalf of the country’s government.

The phone giant said hackers did not access the contents or logs of customer phone calls or text messages, during an industry-wide attack on phone and internet companies.

T-Mobile has severed its connection to the unnamed wireline provider, which it suspects may still be compromised.