One for forum team probably - my old virgin.net e-mail has I think been hacked - spam to my contacts.
Frustrated as when months ago before this I tried to get someone on the phone to help delete it I was told I had to speak to Talk Talk and of course Talk Talk said speak to Virgin. Took a long time to get nowhere.
You have surmised correctly, the Forum Team can take your details by Private message and pass them to the email team to get the address permanently deleted from their system. It might not stop the address from being spoofed (another type of spamming), but it is still a great idea to close it as it should have been done years ago.
Wait here and someone from Virgin Media will contact you. Response time anything from 30 minutes to a few days.
One thing you haven't made explicit - are you no longer a VM broadband customer?