diff --git a/payment/creditcall.go b/payment/creditcall.go
index be842a2..2cae8d3 100644
--- a/payment/creditcall.go
+++ b/payment/creditcall.go
@@ -3,6 +3,7 @@ package payment
 import (
 	"context"
 	"database/sql"
+	"encoding/hex"
 	"encoding/xml"
 	"fmt"
 	"net/url"
@@ -261,8 +262,8 @@ func BuildRedirectURL(result map[string]string) string {
 	// 3) build query params
 	q := url.Values{}
 	q.Set("TxnReference", result["REFERENCE"])
-	q.Set("CardHash", result["CARD_HASH"])
-	q.Set("CardReference", result["CARD_REFERENCE"])
+	q.Set("CardHash", hex.EncodeToString([]byte(result["CARD_HASH"])))
+	q.Set("CardReference", hex.EncodeToString([]byte(result["CARD_REFERENCE"])))
 
 	// only append these when non-approved
 	if msgType != "" {