There is an option to set the “White List” mode, which will not allow incoming calls to the app, except for a list of predefined numbers.
How to set the status: Enter the main menu >> Settings >> Block numbers
Select “White List” mode
To add numbers to the allowed list, press +, add a number and save it. A list of numbers that can dial the app will appear at the bottom of the “Block numbers” page.
You can also add numbers from a call log by marking the line and selecting “Add to black list” when the app is in “White lists” mode.