By default, calls are made via SIM card 1, but the Samsung device can also be configured to use SIM card 2, or the device always makes a query before a call.

Note: The default SIM card for calls can also be changed via the status bar.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Connections
Step 3:  Tap on  SIM card manager
Step 4:  Tap on  Calls
Step 5:  Choose between  Ask always ,  SIM 1  and  SIM 2
  1. Open the Settings
  2. Tap on Connections
  3. Tap on SIM card manager
  4. Tap on Calls
  5. Choose between Ask always, SIM 1 and SIM 2

Samsung Instructions