To the FBI.
Selling data to law enforcement has been quite the cash cow for AT&T, and this scheme has only recently come to light. Their surveillance-for-profit program, "Hemisphere," which sounds like a Bond villain came up with it, began as a partnership with the DEA to assist in counternarcotics investigations. That seems like a rather philanthropic thing to do, but it didn't take long for the company to figure out that selling customer data access to local agencies for taxpayer money was a much more profitable venture. So they began keeping detailed records (much longer than other service providers do) for exactly this purpose, with privacy concerns given about as much reasoned consideration as an impatient customer service rep might give an irate caller with an early termination fee complaint.
"And complaining about it has incurred a 'Go To Hell, Steve' surcharge. Wanna keep going?"
Sure, they're helping to crack important cases (up to and including murder), but that's only part of their shitty and expensive package deal -- which is so typically AT&T. Regional police and sheriffs have to pony up anywhere between $100,000 to a million bucks to get their hands on that sweet Hemisphere goodness. And to show how the costs can balloon, let's use Harris County, Texas as an example. Their first payment to AT&T in 2007 was about $78,000 for data access. They must have been thrilled with their purchase, too, because four years later, they happily forked over $940,000 for the same privilege. But it's all worth it to the cops, since buying information from AT&T means they don't need to bother with silly formalities like search warrants. All they have to present is an administrative subpoena, and that doesn't even require probable cause.