Nevermind... figured it out.  I needed to access the profile information in a different way.

   // set payment profile for customer

    $paymentProfile = new AnetAPI\PaymentProfileType();

    $paymentProfile->setpaymentProfileId( $customerPaymentProfileId );

    // set customer profile

    $customerProfile = new AnetAPI\CustomerProfilePaymentType();

    $customerProfile->setCustomerProfileId( $customerProfileId );

    $customerProfile->setPaymentProfile( $paymentProfile );

    $transactionRequest = new AnetAPI\TransactionRequestType();

    $transactionRequest->setTransactionType( "refundTransaction"); 

    $transactionRequest->setAmount( $amount );

    $transactionRequest->setProfile( $customerProfile );