One of the biggest upgrades introduced by the iPhone 12 series is 5G support, with all four models supporting both mmWave and sub-6GHz bands. However, it appears that folks who purchase the iPhone 12, iPhone 12 Mini, or the iPhone 12 Pro duo won’t be able to enjoy blazing-fast 5G speeds when dual-SIM functionality is enabled. At least not initially. 

As per an image of a training manual for retailers and carriers that surfaced on Reddit, none of the iPhone 12 models will support 5G when dual-SIM mode is activated. In reply to a FAQ that asks whether 5G works with dual-SIM, the training material says, “When using two lines in Dual SIM mode, 5G data isn’t supported on either line and will fall back to 4G LTE. If customers are using eSIM only and are on a 5G-supported carrier and service plan, they’ll have 5G access.”

What this means is you have to either take out the physical nano-SIM or disable the second line provided by the eSIM system to use 5G on the iPhone 12. Otherwise, both the lines will work only with the 4G LTE standard. This a weird limitation, and will definitely come as a disappointment for users who rely on dual-SIM to keep their personal and professional numbers separate. However, it appears that the issue is temporary and will soon be fixed via a software update.

The Reddit user who originally shared the user manual’s screenshot mentioned that Apple will roll out an update later this year that will end the aforementioned limitation and will allow users to enjoy 5G in dual-SIM mode. Notably, Apple’s own support page talking about dual-SIM and eSIM functionality doesn’t mention this limitation at all.  But then, the aforesaid page also lacks any mention of the iPhone 12 series and will likely be updated once the iPhone 12 starts shipping.