Unable to manage child account

I created an EA child account for my kid, then I purchased XBOX game pass and connected the xbox account to the child account via the EA Play app. Then I saw that the child account was unable to install and play any games available via game pass (mainly FC25). I then realised the kid already had an EA account from before that wasnt a "child account", so I figured I could connect the xbox account to that instead. Now here's the problem; I can't figure out how to unlink the xbox account from the child account as there is nowhere to manage this account. The account only has a username and password, but on ea.com you have to login with an email or phone number. When I log into my own account that I created the child account via, the child account is not listed in the manage family section in ea.com when I am logged in, and I can't add the child account either as I need to use an email to add the child account 🤷🏻‍♂️

If I login to the EA app with the child account, there is only a few app settings available. No account settings.

TLDR; how can I manage a child account created with no email address?