I’ve completed implementing Firebase Auth with phone verification .
It has no problems until this error shows up.

[SmsRetrieverHelper] SMS verification code request failed: unknown status code: 17499 BILLING_NOT_ENABLED

I have implemented Firebase authentication in my android application. I want to implement Authentication with OTP verification but when I try to authenticate with OTP it won’t send OTP. Instead of OTP I get an error:

It seems to me that Firebase User ID must stable for the same device and the same application. I can not understand why User ID changing.

It seems to me that Firebase User ID must stable for the same device and the same application. I can not understand why User ID changing.

When I log out of the account and log in to another account, I log in to the previous account. When I log out, close and open the application, I can log in to another account properly. There is automatic login in the application. The interesting thing is that when I open and close the application when it logs into the wrong account, it logs into the correct account.

When I try to delete anonymous user by calling

How to check if the email address exists or not and only if exists than send the email. In this moment an email is sent even if the entered email address is not assigned to a registered account (task.isSuccessful() return always true).