This error happens because phone auth works differently on React Native than on web. On web you can call signInWithPhoneNumber directly, but on mobile it needs extra setup. If you’re using Expo managed workflow, you’ll need expo-firebase-recaptcha for verification. If you’re on a custom dev build or bare workflow, the easier option is to use @react-native-firebase/auth, which handles SMS sign-in natively. So i have seen your code isn’t wrong it’s just that the method you’re using only works on web unless you add the right setup for React Native.