Unable to delete my virginmedia email addresses

I'm trying to delete my primary and secondary email address that I used with Virginmedia until I terminated my account in December 2023. Despite my account being closed down, the email addresses still work and people are still sending email to them (despite me telling them not to). 
I've just spent half an hour on the phone to VM customer service asking them to delete my email addresses.
They just told me it was my personal email address and I could close it down. I told them that my account closed 6 months ago and I am unable to log in to delete my email addresses. They told me to ignore any emails sent to these addresses - I told them that people are still sending emails to them (despite me asking them not to) and all I want to do was to delete the email addresses. Their final response was to ask me to get friends or family to show me how to delete my email addresses - I said that I'd been the phone to VM for 30 minutes and they were unable to do it, so I'm not holding out any hope on friends and family being able to delete an email address from the VM mail servers.
I am unable to log in to my old VM account and just want VM to delete my old email addresses - but VM seem unable to do this. What do I need to do to delete my old addresses?