Another close and old .ntlworld account issue

We joined Virgin for their TV/internet/phone cable service long ago when we lived in the .ntl world.  We moved in 2009 and Virgin were not able to offer a service in our new home, no cable there, so we left them. I have been plagued with Spam/Phishing emails forwarded to my current email address from an old .ntlworld one, but cannot stop it as Virgin removed our Web access. I also notice that many of these emails are also copied to the same, user unknown third party addresses.  The rate of these rogue emails has increased exponentially recently.

Strangely I recently managed to access the email account on an app using my original password, even though that had been changed a couple of times, but Virgin Media webmail does not recognise any of my details. Unfortunately the app access does not enable me to stop the forwarding or close the account.

I have just had a long web chat with an agent asking that our .ntlworld.com email accounts be closed, given him the original Virgin account numbers, copious details etc. and he says the account doesn't exist so they cannot close the email service. So this floating account with my details being open to other unknown users with no ability to stop it is a serious security breach and probably a breach of the GDPR regulations due to Virgin divesting themselves of responsibility and control.

If there is no immediate solution, my next step will be Ofcom.