We use Firebase Phone auth in this to verify Phone numbers, therefore you have to create a New Project on Firebase by going to Firebase Console then sign in using your google account if your'e not signed in, then create a new Project and set the name you like for the project, then:

google-services.json. it will download a .json file we will use it later 
google-services.json and paste it in the path
EqualChat - Android App\app\ to make sure that your app is linked with your Firebase Projectnext up you have to Enable Phone Authentication in Firebase Console by going to :

After that you have to Upgrade to Blaze Plan in Firebase Console by clicking at the bottom left.