It's sent to the email address registered on your account.
If you don't have access to that email address/inbox then see here:
What happens if I don’t have access to my registered email? : You’ll need access to your registered email to reset your password and complete verification when signing in. If you can’t access it, contact our Care team and we’ll help you get back into your account.
To contact 48 support see the links in my signature below.
