User manual

You can set the default number to be used for making calls or choose a number when making
a call. Similarly, you can choose which SIM card is to be used for mobile data.
Use the secondary data SIM for mobile data during calls
If you use the primary SIM card for Internet access, this feature lets you use your secondary
SIM card's data temporarily while you are on a VoLTE call using your secondary SIM card.
This ensures an uninterrupted network connection during the call. When the call ends, it will
switch back to the primary SIM card.
Path: Settings - Mobile network - Advanced settings - Use mobile data during calls.