Originally Posted by
Majuki
Even T-Mobile's international roaming benefit is starting to lose its edge. We're rapidly moving in a direction where eSIM support will be ubiquitous across all devices and carriers with the option of having multiple active profiles simultaneously. Services like Airalo allow you to get an eSIM up and running remotely and be up and running as soon as you're on the ground at the destination. It is then possible to use DIGITS or another VoIP service to send and receive calls using your primary mobile number.
get an iphone - they support DSDV, so you can use your regular call over the data connection of 2nd sim (similar to wifi calling, where the regular call is over wifi)
just small scenario if data drops, call may switch to network (incurring fees). probably can force sim to connect to unauthorized network so network connection wont happen
https://support.apple.com/en-us/HT209044
scroll down to Learn about Dual SIM status icons
With Allow Cellular Data Switching turned on, the status bar shows that Carrier 1 is using 5G, and Carrier 2 is using the cellular data of Carrier 1 and has Wi-Fi calling enabled.
unfortunately with androids, this support isn't clear (which phones have DSDV)
https://www.techmesto.com/dual-sim-w...ported-phones/