public function transferCredit(Transfer $transfer)
    {
        $transfer->setRequiredFields(array(
            'amount',
            'linkedAccount',
            'merchantRefNum',
        ));
        $transfer->setOptionalFields(array(
            'detail',
            'dupCheck',
        ));

        $request = new Request(array(
               'method' => Request::POST,
               'uri' => $this->prepareURI($this->creditPath),
               'body' => $transfer
           ));

        $response = $this->client->processRequest($request);

        return new Transfer($response);
    }