diff --git a/frontend/src/pages/contracts/ContractDetail.tsx b/frontend/src/pages/contracts/ContractDetail.tsx
index 1845af40..d295da0a 100644
--- a/frontend/src/pages/contracts/ContractDetail.tsx
+++ b/frontend/src/pages/contracts/ContractDetail.tsx
@@ -15,6 +15,7 @@ import Input from '../../components/ui/Input';
 import Modal from '../../components/ui/Modal';
 import FileUpload from '../../components/ui/FileUpload';
 import { Edit, Trash2, Copy, Eye, EyeOff, ArrowLeft, ArrowRight, Download, ExternalLink, Plus, ChevronDown, ChevronUp, Gauge, CheckCircle, Circle, ClipboardList, MessageSquare, Calculator, Info, X, BellOff, Lock, Shield, FileText, Images } from 'lucide-react';
+import toast from 'react-hot-toast';
 import JpgToPdfModal from '../../components/ui/JpgToPdfModal';
 import { calculateConsumption, calculateCosts, calculateMultiMeterConsumption } from '../../utils/energyCalculations';
 import CopyButton, { CopyableBlock } from '../../components/ui/CopyButton';
@@ -122,19 +123,27 @@ function SimCardDisplay({ simCard }: { simCard: SimCard }) {
     if (showCredentials) {
       setShowCredentials(false);
       setCredentials(null);
-    } else {
-      setIsLoading(true);
-      try {
-        const res = await contractApi.getSimCardCredentials(simCard.id);
-        if (res.data) {
-          setCredentials(res.data);
-          setShowCredentials(true);
-        }
-      } catch (err) {
-        alert('PIN/PUK konnte nicht geladen werden');
-      } finally {
-        setIsLoading(false);
+      return;
+    }
+    setIsLoading(true);
+    try {
+      const res = await contractApi.getSimCardCredentials(simCard.id);
+      if (!res?.data) {
+        toast.error('Backend lieferte keine PIN/PUK-Daten zurück');
+        return;
       }
+      if (!res.data.pin && !res.data.puk) {
+        toast('Für diese SIM sind keine PIN/PUK hinterlegt', { icon: 'ℹ️' });
+      }
+      setCredentials(res.data);
+      setShowCredentials(true);
+    } catch (err) {
+      const msg = err instanceof Error ? err.message : 'Unbekannter Fehler';
+      // eslint-disable-next-line no-console
+      console.error('[SimCardDisplay] getSimCardCredentials failed:', err);
+      toast.error(`PIN/PUK konnte nicht geladen werden: ${msg}`);
+    } finally {
+      setIsLoading(false);
     }
   };