I'll be brief. No one - not you or VM can delete your primary e-mail address. It is too closely tied to the rest of the VM's systems that give you access to on-line billing etc via My Virginmedia.
In these circumstances you MUST follow this advice to secure the account:
https://www.virginmedia.com/help/virgin-media-mail-my-email-has-been-hacked
There is one thing that might give you some comfort. If you don't access the address in any way for 150 consecutive days VM will close it for e-mail purposes but it will still be valid for My Virginmedia sign-on etc. You can then use any other e-mail address for your day-to-day transactions. Remember to change your contact address for VM communications in MY Virginmedia or you won't get bill notifications etc.
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
Click to learn more about VIP
Use Kudos to say thanks
Mark as Helpful Answer if I've helped