public function sendMessage($recipient, $message, array $params = null)
    {
        $sender = $this->createMessageSender();

        $msg = $this->createMessage($recipient, $message);

        $sender->setMessage($msg);
        if ($params) {
            $sender->setParams($params);
        }
        $response = $sender->send($this->testMode);
        $this->validateResponse($response);

        return $sender->extractResponse($response);
    }