Q: I just upgraded my iPhone but now cannot activate it because I don’t know the carrier that it’s locked to. How can I find out which SIM/carrier that this iPhone is locked to?
A: Unfortunately, there’s no straightforward way to do this as it’s actually based only on your iPhone’s International Mobile Station Equipment Identity number, or IMEI. Unlike most other cellular phones, Apple doesn’t allow any carrier-specific branding on either the hardware or software, so there’s nothing obvious you would find on an iPhone that would indicate which carrier it came from.
If you know anybody who uses an iPhone on an alternate network that your iPhone might possibly be locked to, you could simply try popping in their SIM card and see what happens. This is obviously a trial-and-error method, and may not be practical if you’ve purchased the iPhone from an online site, since it could conceivably be locked to any carrier in the world.
Another option would be to try visiting a local Apple Store, where they might be able to look up your iPhone’s IMEI number and let you know which carrier it is locked to. Apple does have this information in a database somewhere, however Apple Retail staff may not typically be able to look up or provide this information.
If none of these methods are practical, you can try using the online service IMEI.info, where you can enter your IMEI number to get more information about your iPhone. The site will allow you to determine basic information about your device—such as whether it’s locked or unlocked—at no cost, although you will need to register for an account to do so. There is a $3 charge, however, to determine what carrier your device is actually locked to.
You can determine the IMEI number of your iPhone in one of several ways. Dialing “*#06#” from the keypad in the Phone app will display your IMEI number to you,
You can also find it in the Settings app under General, About. Note that the carrier name shown on this screen simply represents the SIM card that is inserted into your iPhone (if any), not the carrier that your iPhone is actually locked to.
You can also obtain the IMEI via iTunes by connecting your iPhone to your computer. Bring up the “Summary” screen for your device in iTunes and click on the “Phone Number” field and it will switch to show the IMEI.