Zoho Writer Merge and Sign delivery via EMAIL and SMS

Zoho Writer Merge and Sign delivery via EMAIL and SMS

How do we use Writer API Merge and Sign that will delivery the document via Email and SMS.

I cannot find information on the documentation. 

I tried formatting the signer data like this

[
    "recipient_1" => "test@email.com"
    "recipient_name" => "Test Name"
    "action_type" => "sign"
    "recipient_phonenumber" => "123456789"
    "recipient_countrycode" => "+61"
    "language" => "en"
]


But it doesn't work, and when I check the contact added inside Zoho sign, the country code and phone number is not even added to the contact.

Appreciate any help