@POST("/request.php")
void sendRequest(@QueryMap Map<String, String> parameters, retrofit.Callback<RequestSendResponse> callback);

public static Map<String, String> parametersSendRequest(Context sender, Request request)
{
    Map <String, String> parameters = new HashMap<>();
    Operator operator = AppConfig.config().operator;

    parameters.put("user_name", request.user_name);
    parameters.put("user_surname", request.user_surname);
    parameters.put("user_gender", request.user_gender);
    parameters.put("user_relationship", request.user_relationship);
    parameters.put("user_dob", request.user_dob);
    parameters.put("operator_name", operator.name);
    parameters.put("request_photoid", request.request_photoid);
    parameters.put("request_user_content", request.request_user_content);
    parameters.put("request_title", request.request_title);
    parameters.put("uuid", UUID(sender));
    parameters.put("response_type", "json");
    parameters.put("platform", "android");
    parameters.put("mode", "send");

    return parameters;
}

{"POST":[],"GET":{"operator_name":....}}