I have just signed up for a pay monthly sim only deal. I previously had a payg sim which my son used. It's no longer in use. I already have an account which was set up when that sim was active. I'm trying to set up an account to view my new pay monthly bills but can't set up a new account as I already have one attached to my email and can't add my new number to my existing account. How do i get around this in order to manage my account?