Primary account login

The first email address I had was a ntlworld.com address, which always used to be the primary account. This isn’t recognised when I try to view my bills. Neither is the first virginmedia.com I created. I’ve different emails for different things, but have no idea anymore which is the primary account as none seem to be recognised. It lets me lay the bill without issue but not actually view it. How do I confirm which is my primary? How do I change it?