Hey there @ardhi, I apologize for the delay in response. I know it has been some time since you reported this question but I wanted to reach out and share with you our documentation on this front along with a blog article that was built in 2017 that references this exact use case with Whatsapp and passwordless sms.
If this hurdle is something you are still facing in the wild today, please give these a look and let me know if they help you on your quest or if you have any additional questions.
I will keep this topic open for 10 days unless I hear otherwise from you. Once again, I apologize for the delay in getting back to you.