How to activate or deactivate the on / off functions?

- For calls and messages:

In the app, open the menu with the icon at the top left.
Press "Options" under the number.
From here you can turn calls and messages on or off using the corresponding buttons.

- For voicemail:

Open the app and go to the "Voicemail" tab.
Tap the microphone icon.
Select a number, then use the toggle switch at the top to turn voicemail on or off.