getUrl content type

getUrl content type

Hi
i have a problem, i have tried to call a my webservice which return a json object.
So this services is authenticated and return a json object.
That s my code :

string GetShipmentInfo(int orderReference)
{
header = Map();
username = "myUsername";
pwd = "";
Base64Encoded = zoho.encryption.base64Encode(username + ":" + pwd);
header.put("Content-Type","application/json");
header.put("Authorization","Basic " + Base64Encoded);

response = getUrl("https://mysite/API/GetOrderData/" + orderReference,header,true);
return response;
}

So the call work but didn't return a JSON object,it return a text/html, but in header i had set the content type to JSON.
Please help me