Credit reporting agency Experian on Thursday said hackers managed to breach the security of one of their servers containing T-Mobile customer data. Personal information belonging to around 15 million wireless customers was stolen, the company said.

T-Mobile CEO John Legere said he is incredibly angry about the data breach and will institute a thorough review of their relationship with Experian but right now, his top concern and first focus is assisting any and all consumers affected. Legere clarified that neither T-Mobile’s systems nor network were part of the intrusion and it didn’t involve any payment card numbers or bank account information.

Hackers made away with names, addresses, social security numbers, driver’s license numbers and passport numbers. Experian said the license and passport numbers were encrypted although the encryption may have also been compromised.

Those that applied for postpaid services or device financing from September 1, 2014 through September 16, 2015 may have been affected. The breach appears to be limited to T-Mobile data as Experian said its consumer credit database wasn’t impacted.

Upon discovery, Experian said it secured the server, initiated an investigation and notified both US and international law enforcement.

The company is offering two years of free credit monitoring services and identity resolution services for those impacted. You can sign up for those services by visiting protectmyID.com.