Change Firebase Data Model class in Flutter

Question

I want to update my firebase data model class. For example

Assume this is my current Data model class

class User {
int id;
String name;
}

And I Want to update it to

class User {
int id;
String name;
String number;
}

The issue is I have already released the app on play store. I have created a web app for backend and an android app for front end. If I update the model then the app will show any data.