The phone wasn't remotely locked; Best Buy's entire new iPhone stock uses "flex activation" which will automatically lock the phone to the first SIM card that's inserted. Fi's primary network is T-Mobile, so for a Fi SIM, this means T-Mobile.

The blame here lies on Best Buy (for not making it clear that this occurs) and Apple (for designing and supporting "flex activation" -- which will still carrier-lock the phone even if a MVNO SIM, such as a Fi SIM, is inserted).

To simplify: Best Buy sells locked phones.

The locking is already there, but the operator is chosen at the activation so that Best Buy can sell one model for any operator.

So the blame is actually Apple’s for blindly allowing this behavior, Best Buy’s for not advertising it, T-Mobile’s for allowing this through MNVO’s, and Google’s for not knowing that this happens and not allowing unlocks.

And they said my Node dependency tree was a mess!

Agree. Such practice was dumb and incessive. If it was made clear, why would someone buy it in the first place?

But what is the point of this flex activation scheme?

Easier inventory management for stores like Best Buy. Instead of having to carry SKUs for the T-Mobile, AT&T, Verizon, etc. carrier-locked variant of each phone (which, I'll admit results in some combinatorial explosion), they can carry 1 SKU for each truly different hardware configuration. Then it magically "becomes" an AT&T locked phone when they insert the SIM in the store.

If you buy it subsidized or through a carrier payment plan, this works as intended (and they'll refuse to let you have the phone before the SIM is inserted). If you meant to buy an unlocked phone, you've been given an annoying lesson to buy directly from the manufacturer.

Ah I see, thanks for the explanation.

Beyond Google Fi and T-Mobile, this story has made me suddenly much more apprehensive about picking up SIM cards from some local MVNO when traveling. What’s to stop a local operator from locking my phone and leaving an unpleasant surprise waiting when I get home?

And now I also have to wonder: do eSIMs have the same vulnerability to bad-actor carriers? Is this a risk with any of the companies Airalo has partnered with?

It can only ever happen when the phone is first activated. So if you have already used the phone with another carrier's SIM card, you are good to go.

It's not an issue of the carrier locking it. Right now there is no mechanisim for an arbitrary carrier to issue a lock command through SIM or otherwise. The issue is that the iPhone hardware itself was watching for insertion of a SIM and locking itself to the first SIM inserted.

An unlocked mobile device cannot be locked to a carrier because the SIM lock mechanism is disabled, which basically tells me he got a phone that he thought was unlocked but was actually locked to T-Mobile.

Keep in mind that Apple’s modern SIM lock implementation is built into the OS and has nothing to do with the modem being locked, so all assumptions about modem locks no longer apply.

Apple’s SIM lock “feature” checks in with Apple over the internet (including over the disallowed SIM, since the modem itself is always unlocked) and refuses to let you proceed if the current SIM doesn’t match the policy returned by the backend.

Obviously the policy can be changed at any time. This is also how this “flex carrier lock” is implemented.

> An unlocked mobile device cannot be locked to a carrier because the SIM lock mechanism is disabled

If it's a Best Buy "unlocked" iPhone it can! It was unlocked when he bought it, but locked onto the first network it was activated (Fi is T-Mobile[1] MVNO)

1. and AT&T too for fully supported Fi phones - you can get seamlessly handed over between T-Mobile, AT&T and wifi. However, iPhone are not fully supported, so they exclusively use T-Mobile.

I would expect this to be the case. If they can remotely unlock it, they should be able to lock it as well.

It really depends on what you mean by "should be able". If you mean "I would expect it to be physically possible to implement something like this", then obviously. If you mean "I think manufacturers should design phones in a manner that allows this"... that one is not so obvious to me.

They're cell phone carriers. They're going to want as much control as possible regardless of how many engineers and customers whine about it.

I wonder if the obvious solution would be a warranty return (if bought in a country/state with reasonable customer protection laws).