Welcome to the community and thanks for taking the time to post on our forums.
I'm sorry to hear of the issues that you're having at the moment with your old email account, this sounds like the account has been orphaned, when you left us, as there was no active broadband account for it to work from. We would need to delete this account from our servers as we cannot recover orphaned.
Your mailbox should have been deleted 90 days after you disconnected with us but this can sometimes be missed.
Please can you send me a private message confirming the email address this concerns and we can get this raised with our IT team to be removed.