"While these cybersecurity breaches may not be systemic in nature, their frequency of occurrence at T-Mobile is an alarming outlier relative to telecom peers," said Neil Mack, senior analyst for Moody's Investors Service.
A spokesperson for the U.S. Federal Communications Commission (FCC) said the regulator had opened an investigation into the incident.
Here's another article on this:
T-Mobile data breach exposes about 37 mln accounts
https://www.reuters.com/technology/t-mobile-says-investigating-data-breach-affecting-37-mln-accounts-2023-01-19/