How can I disable only specific UIDs in firebase authentication?

I am using React native. I want to prevent logging in with a specific UID among UIDs that have anonymous login in my app.

However, Even if I try to disable anonymous login in the firebase console, it keeps logging in.

i tried like this

However, if I keep running the app, i can still be logged in. What should I do?

this is my code

    import auth from '@react-native-firebase/auth';



    useEffect(() => {
        auth()
        .signInAnonymously()
        .then(() => {
            console.log('User signed in anonymously');

        })
        .catch(error => {

            if (error.code === 'auth/operation-not-allowed') {
            console.log('Enable anonymous in your firebase console.');
            }
            console.log("error:", error);
            console.error(error);
        });
    }, []);



    function onAuthStateChanged(user) {
        setUser(user);
        if (initializing) setInitializing(false);
    }

    useEffect(() => {
        const subscriber = auth().onAuthStateChanged(onAuthStateChanged);
        return subscriber; // unsubscribe on unmount
    }, []);