Welcome to the Virgin Media Community, I'm sorry for the problems you've been experiencing with your service recently.
I'd like to check this from our end for you, so I can do that could you respond to the private message I've sent with the requested information? You can view the message by clicking the envelope on the top right of this page.
Very sorry to understand that you are still having some issues with your Voicemail service after we checked it for you last month.
What happens when you dial 1571 - are you getting the voicemail box ok along with any options? The first time you dial, you’ll hear a short message telling you how to use it. As soon as you log in after this initial log in, the voicemail system tells you which keys to press to manage your mailbox. If you don’t have any messages, you won’t hear these.
Do you have your own answering machine built into your handset at all?
I'll also go ahead and do some further internal checks from this end if you could pop me a reply when you can and we'll go from there.