public function reverseAuth(CardPayments\AuthorizationReversal $authReversal)
    {
        $authReversal->setRequiredFields(array('authorizationID'));
        $authReversal->checkRequiredFields();
        $authReversal->setRequiredFields(array('merchantRefNum'));
        $authReversal->setOptionalFields(array(
             'amount',
             'dupCheck'
        ));

        $request = new Request(array(
             'method' => Request::POST,
             'uri' => $this->prepareURI("/auths/" . $authReversal->authorizationID . "/voidauths"),
             'body' => $authReversal
        ));
        $response = $this->client->processRequest($request);

        return new CardPayments\AuthorizationReversal($response);
    }