https://www.bleepingcomputer.com/news/security/t-mobile-says-new-data-breach-caused-by-sim-swap-attacks/

T-Mobile confirmed that recent reports of a new data breach are linked to notifications sent to a "very small number of customers" who fell victim to SIM swap attacks.

"We informed a very small number of customers that the SIM card assigned to a mobile number on their account may have been illegally reassigned or limited account information was viewed," a T-Mobile spokesperson told BleepingComputer.