Fix Registration and authentication bug in Flutter with Firestore application

Hi i need an expientence flutter and Google firestore developer to fix a bug in the Registration and authentication At the moment i after registration we are supposed to send otp for verification before user is saved in firestore DB. The registration form does not have a place for email so we generate a fake email to match the phone number which means we need to find a way to send OTP to the phone numbers and use the same for password rest. if anyone has this experience he should bid. i need to fix this before Monday so the person should be ready to star work now