I want to change my Firefox account primary email address from -----@xxxxx.net to -----@yyyyy.com. When I enter @yyyy.com as the secondary email address in the page https://accounts.firefox.com/settings/emails the red notice "Account already exists" pops up. How can I ensure that the yyyyy.com email address is used as the primary email address and the xxxxx.net address becomes the secondary address? Thank you