Hi @Robbert2024,
Each line comes with a voicemail box built-in and you can access it in multiple ways. Since you mention not having any handsets I would assume that you are using the GoTo App on your computer?
The first thing I would check and confirm is that your voicemail is not set to delete the message after it is forwarded by email. That way a copy of the voicemail will still be accessible in the desktop app.