To disable the authentication method for passwordless phone sign-in, complete the following steps:
- Sign in to the Azure portal with a global administrator account.
- Search for and select Azure Active Directory, then browse to Security > Authentication methods > Authentication method policy (Preview)
- Under Passwordless phone sign-in, choose the following options:
- Enable - Yes or No (Select No to disable)
- Target - All users or Select users
- To apply the new policy, select Save.
Also, please elaborate what exactly you meant by 'use as a third code authenticator'. I believed you meant, use it as a third party authenticator app. Do correct me if I am wrong.