diff --git a/tests/net/java/com/android/server/net/NetworkStatsSubscriptionsMonitorTest.java b/tests/net/java/com/android/server/net/NetworkStatsSubscriptionsMonitorTest.java
index 8f093779da..6d2c7dc39f 100644
--- a/tests/net/java/com/android/server/net/NetworkStatsSubscriptionsMonitorTest.java
+++ b/tests/net/java/com/android/server/net/NetworkStatsSubscriptionsMonitorTest.java
@@ -21,6 +21,7 @@ import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.any;
 import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.clearInvocations;
 import static org.mockito.Mockito.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -150,7 +151,7 @@ public final class NetworkStatsSubscriptionsMonitorTest {
     }
 
     private void assertRatTypeChangedForSub(String subscriberId, int ratType) {
-        assertEquals(mMonitor.getRatTypeForSubscriberId(subscriberId), ratType);
+        assertEquals(ratType, mMonitor.getRatTypeForSubscriberId(subscriberId));
         final ArgumentCaptor<Integer> typeCaptor = ArgumentCaptor.forClass(Integer.class);
         // Verify callback with the subscriberId and the RAT type should be as expected.
         // It will fail if get a callback with an unexpected RAT type.
@@ -302,26 +303,84 @@ public final class NetworkStatsSubscriptionsMonitorTest {
         reset(mDelegate);
 
         // Set IMSI to null again to simulate somehow IMSI is not available, such as
-        // modem crash. Verify service should not unregister listener.
+        // modem crash. Verify service should unregister listener.
         updateSubscriberIdForTestSub(TEST_SUBID1, null);
-        verify(mTelephonyManager, never()).listen(any(), anyInt());
-        assertRatTypeNotChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UMTS);
+        verify(mTelephonyManager, times(1)).listen(eq(ratTypeListenerCaptor.getValue()),
+                eq(PhoneStateListener.LISTEN_NONE));
+        assertRatTypeChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
         reset(mDelegate);
+        clearInvocations(mTelephonyManager);
 
-        // Set RAT type of sim1 to LTE. Verify RAT type of sim1 is still changed even if the IMSI
-        // is not available. The monitor keeps the listener even if the IMSI disappears because
-        // the IMSI can never change for any given subId, therefore even if the IMSI is updated
-        // to null, the monitor should continue accepting updates of the RAT type. However,
-        // telephony is never actually supposed to do this, if the IMSI disappears there should
-        // not be updates, but it's still the right thing to do theoretically.
-        setRatTypeForSub(ratTypeListenerCaptor.getAllValues(), TEST_SUBID1,
+        // Simulate somehow IMSI is back. Verify service will register with
+        // another listener and fire callback accordingly.
+        final ArgumentCaptor<RatTypeListener> ratTypeListenerCaptor2 =
+                ArgumentCaptor.forClass(RatTypeListener.class);
+        updateSubscriberIdForTestSub(TEST_SUBID1, TEST_IMSI1);
+        verify(mTelephonyManager, times(1)).listen(ratTypeListenerCaptor2.capture(),
+                eq(PhoneStateListener.LISTEN_SERVICE_STATE));
+        assertRatTypeNotChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+        reset(mDelegate);
+        clearInvocations(mTelephonyManager);
+
+        // Set RAT type of sim1 to LTE. Verify RAT type of sim1 still works.
+        setRatTypeForSub(ratTypeListenerCaptor2.getAllValues(), TEST_SUBID1,
                 TelephonyManager.NETWORK_TYPE_LTE);
         assertRatTypeChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_LTE);
         reset(mDelegate);
 
         mMonitor.stop();
-        verify(mTelephonyManager, times(1)).listen(eq(ratTypeListenerCaptor.getValue()),
+        verify(mTelephonyManager, times(1)).listen(eq(ratTypeListenerCaptor2.getValue()),
                 eq(PhoneStateListener.LISTEN_NONE));
         assertRatTypeChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
     }
+
+    /**
+     * Verify that when IMSI suddenly changed for a given subId, the service will register a new
+     * listener and unregister the old one, and report changes on updated IMSI. This is for modem
+     * feature that may be enabled for certain carrier, which changes to use a different IMSI while
+     * roaming on certain networks for multi-IMSI SIM cards, but the subId stays the same.
+     */
+    @Test
+    public void testSubscriberIdChanged() {
+        mMonitor.start();
+        // Insert sim1, verify RAT type is NETWORK_TYPE_UNKNOWN, and never get any callback
+        // before changing RAT type.
+        addTestSub(TEST_SUBID1, TEST_IMSI1);
+        final ArgumentCaptor<RatTypeListener> ratTypeListenerCaptor =
+                ArgumentCaptor.forClass(RatTypeListener.class);
+        verify(mTelephonyManager, times(1)).listen(ratTypeListenerCaptor.capture(),
+                eq(PhoneStateListener.LISTEN_SERVICE_STATE));
+        assertRatTypeNotChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+
+        // Set RAT type of sim1 to UMTS.
+        // Verify RAT type of sim1 changes accordingly.
+        setRatTypeForSub(ratTypeListenerCaptor.getAllValues(), TEST_SUBID1,
+                TelephonyManager.NETWORK_TYPE_UMTS);
+        assertRatTypeChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UMTS);
+        reset(mDelegate);
+        clearInvocations(mTelephonyManager);
+
+        // Simulate IMSI of sim1 changed to IMSI2. Verify the service will register with
+        // another listener and remove the old one. The RAT type of new IMSI stays at
+        // NETWORK_TYPE_UNKNOWN until received initial callback from telephony.
+        final ArgumentCaptor<RatTypeListener> ratTypeListenerCaptor2 =
+                ArgumentCaptor.forClass(RatTypeListener.class);
+        updateSubscriberIdForTestSub(TEST_SUBID1, TEST_IMSI2);
+        verify(mTelephonyManager, times(1)).listen(ratTypeListenerCaptor2.capture(),
+                eq(PhoneStateListener.LISTEN_SERVICE_STATE));
+        verify(mTelephonyManager, times(1)).listen(eq(ratTypeListenerCaptor.getValue()),
+                eq(PhoneStateListener.LISTEN_NONE));
+        assertRatTypeChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+        assertRatTypeNotChangedForSub(TEST_IMSI2, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+        reset(mDelegate);
+
+        // Set RAT type of sim1 to UMTS for new listener to simulate the initial callback received
+        // from telephony after registration. Verify RAT type of sim1 changes with IMSI2
+        // accordingly.
+        setRatTypeForSub(ratTypeListenerCaptor2.getAllValues(), TEST_SUBID1,
+                TelephonyManager.NETWORK_TYPE_UMTS);
+        assertRatTypeNotChangedForSub(TEST_IMSI1, TelephonyManager.NETWORK_TYPE_UNKNOWN);
+        assertRatTypeChangedForSub(TEST_IMSI2, TelephonyManager.NETWORK_TYPE_UMTS);
+        reset(mDelegate);
+    }
 }