Credit reporting agency Experian said Thursday that hackers accessed the Social Security numbers, birthdates and other personal information belonging to about 15 million T-Mobile wireless customers.

T-Mobile uses Experian to check the credit of its customers.

Experian said T-Mobile customers who applied for wireless service between Sept. 1, 2013, and Sept. 16, 2015, may have had their information stolen.

Experian said it immediately notified law enforcement authorities after discovering the hack and that “there is no evidence to-date that the data has been used inappropriately.”

The companies said payment card and banking information was not affected.

“I am incredibly angry about this data breach and we will institute a thorough review of our relationship with Experian,” said T-Mobile US Inc. CEO John Legere said in a statement.

There have been a string of high-profile hacks of businesses and other organizations in recent years affecting millions of people, including adultery website Ashley Madison, Sony Pictures, the insurer Anthem, retailers such as Home Depot and Target, eBay and the U.S. Office of Personnel Management.

Nearly 800 data breaches were reported last year by U.S. organizations, according to the Identity Theft Resource Center.