Close my hacked old ntlworld.com email

I had an old ntlworld.com email address from years ago. It was setup to forward emails to my new email address. I've noticed I'm getting logins and sign ups on my ntlworld.com email, which means someone has hacked the account. There's no way to login or reset the ntlworld.com password, so would like the email account to be closed down ASAP. Can someone let me know how to do this as there's no way to do it via support etc. Thanks