You didn't read the guidance...
localhost should work for the fictional numbers set in the console, but not for real numbers.
the warning in the firebase To prevent abuse, new projects currently have a sent SMS daily quota of 10/day. To increase this quota, please add a billing account to the project.
as there is limit 10/day then why it says
{"error":{"code":400,"message":"BILLING_NOT_ENABLED","errors":[{"message":"BILLING_NOT_ENABLED","domain":"global","reason":"invalid"}]}}