I can't tell from your post if you are still a broadband customer?
Follow the advice here to get control of the email addresses again. That is important even if you want to delete them eventually. Secondary addresses can then be deleted by opening the VM billing account, going to my profile, manage accounts and then you can delete addresses. Check the mailbox is gone completely by running the address through mailtester.com. Let us know if it has not worked, VM can then raise a ticket for manual deletion in the back end systems.
The mailbox should have been closed AND deleted automatically 90 days after you finished being a customer (according to VM's own Terms and Conditions). But the process fails all too often and leaves the former customer vulnerable to hacking and theft of personal and financial details (IMO, someone should definitely claim for damages from VM or complain to ICO!)
Only VM staff can raise a ticket to get the mailbox deleted manually. The friendly Forum Team will visit this thread in the next few hours (or days?) and then take your personal details by private message.
When they say it is done, you can verify the mailbox is gone by running the email address(es) through mailtester.com. Best wishes to you.
Thanks. I am no longer a Virgin Media customer and it has been well over 90 days. I’d appreciate someone from Virgin Media team to contact me about closing these addresses - they are old ntlworld ones do a legacy from well before VM took over