[nathana]

As far as I know, there is no standards-based mechanism for doing so as SIMs predate packetized cellular data over GSM, so the concept of the APN was not around to be "baked into" the GSM SIM when it was first conceived, and the SIM has seemingly not been spec-bumped since to support it. I have never run into a GSM phone that can automatically pull its APN configuration from the carrier network or from a SIM; it's either been pre-configured for you in the ROM (in the case of locked phones) or manually configurable (in the case of unlocked phones).

Apple provides an automatic APN configuration subsystem that the carriers control, but it is completely proprietary to iPhone, and it is in fact this exact subsystem that is causing me grief.

Some final notes of clarification:

1) Straight Talk isn't a "small carrier" (read: regional carrier with "rural" possibly implied) in the U.S., at least in terms of the size of the network itself. In fact, Straight Talk doesn't actually own any of their own infrastructure: they ride the nationwide AT&T network.

2) This proprietary iPhone automatic APN configuration system is used on ALL iPhones worldwide, regardless of carrier. So this has nothing to do with how carriers in the U.S. do or do not accomplish this vs. how you think other carriers outside the U.S. accomplish this. If you own an iPhone and have a SIM card in it that was issued by a carrier anywhere in the world that Apple has a contractual relationship with, your phone was configured this way, and you could run into the same problem I documented here depending on the situation.

[ricardobeat]

My original carrier is from Brazil, and I can't see their APN settings, but I've used three SIMs in Europe from different carriers and they all worked seamlessly, and was able to look into the APN settings for at least one of them (Wind, I think).

To me this looks like an issue of Straight Talk failing to fulfill their job as a carrier, or AT&T not providing the necessary access to their resellers. If you're going to sell mobile plans you should have the infrastructure to support it (third-party or not).

[nathana]

Right, so the Brazilian SIM card was issued by a carrier that has a carrier profile included with iOS that is set to block access to that menu, while the European SIM cards you have either were issued by carriers with carrier profiles in iOS that don't block access to that menu, or those European SIM cards were issued by a carrier or carriers that the iPhone knows absolutely nothing about (no built-in carrier profile(s)).

In my case (and in the case of some other customers of other MVNOs), my carrier, Straight Talk, is really just a company that buys wholesale access to AT&T's network and then resells it as a prepaid service to customers. Thus a Straight Talk SIM card looks identical to an AT&T SIM card to the iPhone. And AT&T's iOS carrier profile blocks access to the APN editing submenu. So my situation is different from yours because in your case, your Brazilian service provider and your European service providers had no corporate connections with each other, nor did they share a singular common network, as is the case with AT&T and Straight Talk.

There is next-to-nothing Straight Talk can do about this, at least without both AT&T's and Apple's co-operation.