Apple's iOS 12.1 update brought digital eSim support to the iPhone XS, XS Max, and XR on Tuesday, but US carriers won't support the feature until later in the year due to reported technical problems.
eSIM is the software-based version of the traditional plastic chip that identifies you to your carrier, and Apple highlighted it and the new iPhones' dual SIM capabilities during the company's September event.
This allows iPhone users to switch between two numbers on the same device.
However, Verizon, AT&T and T-Mobile all won't support eSIM immediately, according to MacRumors, which highlighted technical issues the feature creates.
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Verizon customers suffer from performance problems if they activate eSIMs from other companies, the carrier confirmed in a statement.
"If you are a Verizon customer and you activate another carrier's service on your iPhone's eSIM, your Verizon service will be degraded due to the current software configuration," said Kelly L. Crummey, the company's director of corporate communications, in an email.
"Based on our discussions with Apple, we believe these concerns will be resolved quickly and you should be able to add our great Verizon service on your secondary line before the end of the year."
Crummey noted that Verizon won't activate its "service on any eSIM" until the secondary line can deliver the full suite.
AT&T is reportedly telling customers that eSIM support is delayed until late 2018 because it causes problems linked to visual voicemail. T-Mobile told PCMag that it's working on eSIM support and that it'll be available "when its software is ready."
Sprint, the fourth major US carrier, isn't included on Apple's list of those supporting eSIM, but said it will offer the feature at some point.
Neither AT&T nor T-Mobile immediately responded to requests for comment.
First published at 6:25 a.m. PT.
Updated at 7:31 a.m. PT: Added Verizon statement.
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