Error from JustCall API

Hi Everyone

I am attempting to use the JustCall API to send messages.

I have the following that I am sending to the API:

message_Map = Map();

message_Map.put("body","testing message");

message_Map.put("justcall_number","+61483942873");

message_Map.put("contact_number","+61413152929");

header_Map = Map();

header_Map.put("accept","application/json");

header_Map.put("Authorization","758da02e78290bc0d38e68e63d:26b444a910ce4ed41934bf80"); //This has been modified so not the actual authorisation being disclosed.

message_JustCall = invokeurl

[

url :"https://api.justcall.io/v2/texts/new"

type :POST

parameters:message_Map

headers:header_Map

];

And I am receiving the following response from the API.

{"statusCode":415,"message":"Unsupported Media Type: application/x-www-form-urlencoded"}

Before I ask JustCall, I thought someone on here might be able to see something I am doing wrong with the request I am sending.

Thanks for your help.

Carl