The new iPhones introduced eSIM technology into the line for the first time. But you can’t use two CDMA SIMs in your device.
eSIM
Apple Watch ECG, iPhone XS eSIM Explained - TMO Daily Observations 2018-09-17
Dave Hamilton and John Martellaro join Jeff Gamet to explore the ECG feature in Apple Watch Series 4, plus they explain dual SIM and eSIM in iPhone XS and iPhone XS Max.
Here Are The Countries That Support eSIM in the new iPhones
An eSIM makes it easier to switch between carriers. But right now only ten countries in the world support it.
China Shuts Down Apple Watch LTE Support Over Tracking Concerns
China shut down LTE support for Apple Watch Series 3, and it’s likely over fears the smartwatch will be used to by other governments to track its citizens.