Dual SIM Improvements
This one didn’t get talked about on stage at all, but from the list of other iOS 13 features shown at the end of the presentation it looks like Apple has some significant improvements planned for users who have more than one SIM setup on their iPhone — whether that’s an eSIM or a physical second SIM card in China.
Last year, Apple debuted Dual SIM Dual Standby (DSDS) with its 2018 iPhone lineup and iOS 12. As word Standby in the name implies, this allows two SIM cards to be provisioned in an iPhone, but only one of them can be in active use at any time — the other one remains on standby. In other words, when you’re on a call on one line, you can’t receive calls on the other — they’ll go straight to voicemail.
With iOS 13, however, it looks like Apple may be switching to Dual SIM Dual Active (DSDA). This will allow both lines to be actively in use, allowing to use data and receive calls on both lines at the same time. DSDA will allow calls to ring through on the second line when you’re on the first,
It also appears that Apple will also allow you to register both of your SIM phone numbers for FaceTime and iMessage, allowing you to receive iMessages and FaceTime calls to either number. Right now on iOS 12, those services can only be enabled on one of your numbers at a time.