public function create($command, $options = array()) {
        $options = new Values($options);

        $data = Values::of(array(
            'Command' => $command,
            'Sim' => $options['sim'],
            'CallbackMethod' => $options['callbackMethod'],
            'CallbackUrl' => $options['callbackUrl'],
            'CommandMode' => $options['commandMode'],
            'IncludeSid' => $options['includeSid'],
            'DeliveryReceiptRequested' => Serialize::booleanToString($options['deliveryReceiptRequested']),
        ));

        $payload = $this->version->create(
            'POST',
            $this->uri,
            array(),
            $data
        );

        return new CommandInstance($this->version, $payload);
    }