diff --git a/src/com/android/phone/CarrierConfigLoader.java b/src/com/android/phone/CarrierConfigLoader.java
index 3d9e0b0..76a16d3 100644
--- a/src/com/android/phone/CarrierConfigLoader.java
+++ b/src/com/android/phone/CarrierConfigLoader.java
@@ -1178,20 +1178,20 @@
 
     @Override
     @NonNull
-    public PersistableBundle getConfigForSubId(int subId, String callingPackage) {
-        return getConfigForSubIdWithFeature(subId, callingPackage, null);
+    public PersistableBundle getConfigForSubId(int subscriptionId, String callingPackage) {
+        return getConfigForSubIdWithFeature(subscriptionId, callingPackage, null);
     }
 
     @Override
     @NonNull
-    public PersistableBundle getConfigForSubIdWithFeature(int subId, String callingPackage,
+    public PersistableBundle getConfigForSubIdWithFeature(int subscriptionId, String callingPackage,
             String callingFeatureId) {
-        if (!TelephonyPermissions.checkCallingOrSelfReadPhoneState(mContext, subId, callingPackage,
-                callingFeatureId, "getCarrierConfig")) {
+        if (!TelephonyPermissions.checkCallingOrSelfReadPhoneState(mContext, subscriptionId,
+                callingPackage, callingFeatureId, "getCarrierConfig")) {
             return new PersistableBundle();
         }
 
-        int phoneId = SubscriptionManager.getPhoneId(subId);
+        int phoneId = SubscriptionManager.getPhoneId(subscriptionId);
         PersistableBundle retConfig = CarrierConfigManager.getDefaultConfig();
         if (SubscriptionManager.isValidPhoneId(phoneId)) {
             PersistableBundle config = mConfigFromDefaultApp[phoneId];
@@ -1235,7 +1235,8 @@
         int phoneId = SubscriptionManager.getPhoneId(subscriptionId);
         if (!SubscriptionManager.isValidPhoneId(phoneId)) {
             logd("Ignore invalid phoneId: " + phoneId + " for subId: " + subscriptionId);
-            return;
+            throw new IllegalArgumentException(
+                    "Invalid phoneId " + phoneId + " for subId " + subscriptionId);
         }
         // Post to run on handler thread on which all states should be confined.
         mHandler.post(() -> {
@@ -1274,17 +1275,18 @@
     }
 
     @Override
-    public void notifyConfigChangedForSubId(int subId) {
-        int phoneId = SubscriptionManager.getPhoneId(subId);
-        if (!SubscriptionManager.isValidPhoneId(phoneId)) {
-            logd("Ignore invalid phoneId: " + phoneId + " for subId: " + subId);
-            return;
-        }
-
+    public void notifyConfigChangedForSubId(int subscriptionId) {
         // Requires the calling app to be either a carrier privileged app for this subId or
         // system privileged app with MODIFY_PHONE_STATE permission.
-        TelephonyPermissions.enforceCallingOrSelfModifyPermissionOrCarrierPrivilege(mContext, subId,
-                "Require carrier privileges or MODIFY_PHONE_STATE permission.");
+        TelephonyPermissions.enforceCallingOrSelfModifyPermissionOrCarrierPrivilege(mContext,
+                subscriptionId, "Require carrier privileges or MODIFY_PHONE_STATE permission.");
+
+        int phoneId = SubscriptionManager.getPhoneId(subscriptionId);
+        if (!SubscriptionManager.isValidPhoneId(phoneId)) {
+            logd("Ignore invalid phoneId: " + phoneId + " for subId: " + subscriptionId);
+            throw new IllegalArgumentException(
+                    "Invalid phoneId " + phoneId + " for subId " + subscriptionId);
+        }
 
         // This method should block until deleting has completed, so that an error which prevents us
         // from clearing the cache is passed back to the carrier app. With the files successfully
@@ -1301,7 +1303,7 @@
                 android.Manifest.permission.MODIFY_PHONE_STATE, null);
         logdWithLocalLog("Update config for phoneId: " + phoneId + " simState: " + simState);
         if (!SubscriptionManager.isValidPhoneId(phoneId)) {
-            return;
+            throw new IllegalArgumentException("Invalid phoneId: " + phoneId);
         }
         // requires Java 7 for switch on string.
         switch (simState) {
diff --git a/tests/src/com/android/phone/CarrierConfigLoaderTest.java b/tests/src/com/android/phone/CarrierConfigLoaderTest.java
index b7d1d70..f58e6cc 100644
--- a/tests/src/com/android/phone/CarrierConfigLoaderTest.java
+++ b/tests/src/com/android/phone/CarrierConfigLoaderTest.java
@@ -28,7 +28,6 @@
 import static org.mockito.ArgumentMatchers.nullable;
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 
 import android.content.Intent;
@@ -149,6 +148,20 @@
     }
 
     /**
+     * Verifies that IllegalArgumentException should throw when call #updateConfigForPhoneId() with
+     * invalid phoneId.
+     */
+    @Test
+    public void testUpdateConfigForPhoneId_invalidPhoneId() throws Exception {
+        mContext.grantPermission(STUB_PERMISSION_ENABLE_ALL);
+
+        assertThrows(IllegalArgumentException.class,
+                () -> mCarrierConfigLoader.updateConfigForPhoneId(
+                        SubscriptionManager.INVALID_PHONE_INDEX,
+                        IccCardConstants.INTENT_VALUE_ICC_ABSENT));
+    }
+
+    /**
      * Verifies that when call #updateConfigForPhoneId() with SIM absence, both carrier config from
      * default app and carrier should be cleared but no-sim config should be loaded.
      */
@@ -219,6 +232,17 @@
     }
 
     /**
+     * Verifies IllegalArgumentException should throw if call #overrideConfig() with invalid subId.
+     */
+    @Test
+    public void testOverrideConfig_invalidSubId() throws Exception {
+        mContext.grantPermission(STUB_PERMISSION_ENABLE_ALL);
+
+        assertThrows(IllegalArgumentException.class, () -> mCarrierConfigLoader.overrideConfig(
+                SubscriptionManager.INVALID_SUBSCRIPTION_ID, new PersistableBundle(), false));
+    }
+
+    /**
      * Verifies that override config is not null when calling #overrideConfig with null bundle.
      */
     @Test
@@ -263,20 +287,16 @@
     }
 
     /**
-     * Verifies that calling #notifyConfigChangedForSubId() with invalid subId will be ignored.
+     * Verifies that IllegalArgumentException should throw when calling
+     * #notifyConfigChangedForSubId() with invalid subId.
      */
     @Test
     public void testNotifyConfigChangedForSubId_invalidSubId() throws Exception {
         mContext.grantPermission(STUB_PERMISSION_ENABLE_ALL);
 
-        mCarrierConfigLoader.notifyConfigChangedForSubId(
-                SubscriptionManager.INVALID_SUBSCRIPTION_ID);
-
-        // verifying the behavior following the permission check is not actually performed.
-        // It against "verify value instead of behavior", but we don't have other alternatives.
-        verify(mPackageManager, never()).getNameForUid(anyInt());
-        verify(mContext, never()).checkCallingOrSelfPermission(
-                eq(android.Manifest.permission.MODIFY_PHONE_STATE));
+        assertThrows(IllegalArgumentException.class,
+                () -> mCarrierConfigLoader.notifyConfigChangedForSubId(
+                        SubscriptionManager.INVALID_SUBSCRIPTION_ID));
     }
 
     // TODO(b/184040111): Enable test case when support disabling carrier privilege