Thanks for posting your question. AT&T branded phones get OS updates over the air from AT&T, and any AT&T phone can only receive an update when it's connected to an active AT&T service on AT&T's network. Unfortunately, since you're using your phone outside of USA with another provider it can not get updates from AT&T. I apologize for any inconvenience.
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I have the same device that was purchased as a test device so it has no cellular service (just wifi). Is there no way to update the OS on this device?
ATT only updates devices with ACTIVE ATT SERVICE in the USA.
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