Personalize my voicemail

(From the mobile application only)

You can choose to leave the default voicemail greeting (Greeting), or personalize it.

To do so, when you're on the home page of your Onoff number, choose the third icon representing a recorder.
This is your voice mailbox.
On the new page, you'll see a little microphone. Click on it and you'll be able to select "Personalize".
Now let yourself be guided to record your greeting.