T-Mobile responded quickly to the data breach and was able to track down the source and put a stop to it within the day of detection. They shut down within 24 hours of detection in order to protect the customers and their security. T-Mobile also contacted law enforcement and is currently investigating the incident. In addition, T-Mobile has implemented additional security measures to prevent further unauthorized access or data breaches. The company has also begun notifying clients whose data may have been breached. T-Mobile said it would offer free credit monitoring and identity protection to those affected in a public press release announcing the breach.
According to The Wall Street Journal, the Federal Communications Commission has opened an investigation into the data breach. "This incident marks yet another data breach in a string of cases at the company, and it's being investigated by FCC," the FCC spokesperson told the publication. This is the eighth time that T-Mobile has been hacked since 2018.
In the last piece with the SEC filing, T-Mobile said that they expect the news not to have any material effect on their operations. In simple terms, T-Mobile doesn't expect their clients to be too upset and decide to take their business elsewhere!