Apple has released iOS 12.1.2. According to the company’s notes, the update:
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Fixes bugs with eSIM activation for the iPhone Xr, iPhone Xs, and iPhone Xs Max;
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Addresses an issue that could affect cellular connectivity in Turkey for the iPhone Xr, iPhone Xs, and iPhone Xs Max.
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You can download iOS 12.1.2 by going to Settings –> General –> Software Update.