Oct. 8, 2012 at 1:45 PM ET
T-Mobile has started stocking the extra-tiny SIM cards that fit the iPhone 5 for those customers who want to bring their unlocked phone to the carrier.
Availability — just like the iPhone 5 itself — is going to vary from city to city. T-Mobile told NBC News the nano-SIM cards will "be available to customers by mid-October."
The nation's fourth-largest carrier, which does not sell the iPhone 5, began a marketing campaign last month to encourage buyers to bring their iPhones, from AT&T or Verizon Wireless, to T-Mobile, touting its unlimited data plan which starts at $69.99 a month for unlocked phones. (Sprint's iPhone 5 will not work on T-Mobile's network.)
The iPhone 5 uses a nano-SIM card, even smaller than the micro-SIM card previously used by Apple. SIM stands for "Subscriber Identity Module," and is a memory chip that holds a user's personal information.
"As a quick reminder, any unlocked AT&T or Verizon iPhone 5 device will work on T-Mobile’s HSPA+ network, along with unlocked iPhone 5 devices sold directly from Apple," wrote David Beren in TmoNews, which describes itself as an "unofficial T-Mobile blog."
But, he said, Apple has "yet to put their unlocked models on sale, which isn’t very surprising given the high demand for carrier models resources are likely focused on producing enough quantity to meet the remaining pre-order demand."
A T-Mobile spokesman confirmed to NBC News that "both Verizon and AT&T unlocked iPhone 5 devices are compatible with our network today and will receive 4G service as we retune our airwaves to turn on 4G service in our iPhone-compatible spectrum in major markets this year."
What that means, in short, is that T-Mobile's 4G network is not the same as Verizon or as AT&T's much faster 4G LTE network. What that also means is if you're thinking of bringing your unlocked iPhone 5, make sure you're in an area where that service is available.