Privacy-First MVNOs: Great Idea, but Worth It?

Phreeli is an MVNO that actually tries to protect your privacy, and I love that it exists; it's doing a good thing, and more carriers should do what they're doing. Unfortunately, however, a privacy-respecting MVNO is only very modestly beneficial for your primary number, especially if you're porting it in, especially if you're porting it in from T-Mobile (whose services Phreeli resells). This is because T-Mobile still handles and sees everything about your actual use of the service; Phreeli only isolates the identity/accounting side (It does a great job of that, but still.). If you ported your number out from T-Mobile itself, T-Mobile still knows exactly who owns that number, so you have not gained privacy, but rather very mild bureaucratic friction. But even in cases where you didn't transfer in from T-Mobile, all it takes is another subpoena — there exist centralizd histories of where your number has been registered (NPAC), your current carrier knows where you transferred in from, and your previous carrier still knows you owned that number, that you transferred it out, and (if they look at a history database like NPAC) that it's remained active without a break in continuity. Advertisers won't do subpoenas to get that information, but they will correlate it to other info they have… and they have that other information. Even if your number was registered fresh at Phreeli and your information does not exist at any other carrier, it's still trivially de-anonymizable if you've ever used it as your number for anything elsewhere. Your friend stored your number in Google/Apple Contacts? Pwned. You had to put your number down for a shipment? Pwned. So Phreeli physically cannot give you actual privacy; it can only increase friction. That is enough to stop lazy bad actors; but anyone with enough motivation or automation can easily blow right past this hurdle without a care.

Nevertheless, more friction is still better than less friction; so let's look at pricing. For Phreely, it's $25 for "Flex" vs $8 for US Mobile (another MVNO)'s equivalent plan ("Light"); or $85 ("Max") for unlimited vs USM's $22.5 ("Unlimited Starter"). That's per month, so it's a huge difference: You're paying hundreds of dollars more per year for moderate security against carrier data breaches and for privacy-through-obscurity (which, as the saying goes, "is not privacy"). That same money could buy you more privacy/security for less: regularly-replaced burner numbers on Phreeli's lowest plan plus a normal number on US Mobile, for example, is more privacy than just having your main number on Phreely and it costs less in aggregate than a single device on Phreeli's unlimited plan. (Though, let's be realistic: very few people have need of burners, and mitigations that are too cumbersome to actually use are not real mitigations.) Or you could get a hardware-encrypted flashdrive to store your data on (vs storing it on your phone). Hell, at a $750/yr delta between Phreeli and US Mobile for unlimited, you could buy a Puri.sm phone and be totally free of Google/Apple's tracking zoo (which definitively wins you a different privacy/security battle of at least equal proportions to the carrier one).
Accordingly, I just cannot see the value of Phreeli over US Mobile unless you use so little data that USM's Unlimited == Phreeli's "Flex" for you; or you're independently wealthy and $750/yr is nothing to you; or you're so principled that these marginal benefits are worth non-marginal cash to you and you've already invested in all the bigger gains available to you. Regardless of your reasons, if you do decide to use Phreeli, please at least start with a fresh number so you get maximum benefit.

(I wrote this to myself while investigating whether to switch to Phreeli, and decided to share it to save others the same cost of research.)