It would be simple to design a cellular data network that didn't tie account holders to devices. Issue access tokens good for e.g. 10 GB of data to the mobile device. Don't store the token in connection with the account. Anyone could buy a prepaid card with tokens for cash at any convenience store. The network identifies the device via the token, which is temporary and anonymous. Telephone routing is done via VoIP which anyone has the option of routing through a VPN.
It's designed the way it is now on purpose, to spy on everyone.
> The "expense" involved in getting warrants approved is a better check on abuse
Except that they don't actually get warrants when they're doing abuse, they just lie about it because the phone company has minimal incentive to check and the victim who does typically isn't notified.
> Of course if your local judge will rubber-stamp blank_document.docx as a proper "warrant" you have a problem again. But that can be addressed in turn.
"Quis custodiet ipsos custodes" is in latin because it was published circa 100 AD. No effective solution to this problem has yet been uncovered.