When you first configured your voicemail, you chose a PIN code for your voicemail. Haven't done so yet? Configure your voicemail and you'll be able to choose a PIN.
If the wrong PIN code is entered three times, your voicemail will automatically be blocked. To reactivate your voicemail send an email to email@example.com stating your phone number. Our helpdesk will then make sure that your voicemail is reactivated as soon as possible.