If you operated an MVNO (Mobile Virtual Network Operator), wouldn't your traffic still be going over AT&T's or some other carrier's network? They'd have access to the information whether you wanted them to or not.

I don't know if they keep billing data for MVNO customers. And, a $500mm/yr MVNO would have the power to negotiate contractual terms which regular individual or business customers wouldn't; not like showing up with pitchforks at exec houses in the middle of the night when violated, but with huge payments required at least.

From my brief research, they still handle all of the SS7 part of things as an MVNO, so even if they don't have 'billing' information, they definitely have the call origination/termination records/history.