Why is it legal for them to collect that data in the first place? Can't sell, abuse, or accidentally leak that which you don't have.
Certainly to resolve customer billing disputes, I'm sure.
https://www.eff.org/cases/hemisphere
https://en.wikipedia.org/wiki/Call_detail_record
http://epic.org/privacy/nsa/Section-215-Order-to-Verizon.pdf