diff --git a/src/com/android/phone/PhoneInterfaceManager.java b/src/com/android/phone/PhoneInterfaceManager.java
index b501892..acf6b39 100755
--- a/src/com/android/phone/PhoneInterfaceManager.java
+++ b/src/com/android/phone/PhoneInterfaceManager.java
@@ -4031,12 +4031,16 @@
             throws RemoteException {
         TelephonyPermissions.enforceCallingOrSelfReadPrecisePhoneStatePermissionOrCarrierPrivilege(
                 mApp, subId, "registerImsRegistrationCallback");
+
+        if (!ImsManager.isImsSupportedOnDevice(mApp)) {
+            throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
+                    "IMS not available on device.");
+        }
         final long token = Binder.clearCallingIdentity();
         try {
-            runUsingImsManagerOrThrow(subId, (ImsFunction<Void>) manager -> {
-                manager.addRegistrationCallbackForSubscription(c, subId);
-                return null;
-            });
+            int slotId = getSlotIndexOrException(subId);
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            ImsManager.getInstance(mApp, slotId).addRegistrationCallbackForSubscription(c, subId);
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode());
         } finally {
@@ -4149,12 +4153,15 @@
             throws RemoteException {
         TelephonyPermissions.enforceCallingOrSelfReadPrecisePhoneStatePermissionOrCarrierPrivilege(
                 mApp, subId, "registerMmTelCapabilityCallback");
+        if (!ImsManager.isImsSupportedOnDevice(mApp)) {
+            throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
+                    "IMS not available on device.");
+        }
         final long token = Binder.clearCallingIdentity();
         try {
-            runUsingImsManagerOrThrow(subId, (ImsFunction<Void>) manager -> {
-                manager.addCapabilitiesCallbackForSubscription(c, subId);
-                return null;
-            });
+            int slotId = getSlotIndexOrException(subId);
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            ImsManager.getInstance(mApp, slotId).addCapabilitiesCallbackForSubscription(c, subId);
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode());
         } finally {
@@ -4194,8 +4201,12 @@
         enforceReadPrivilegedPermission("isCapable");
         final long token = Binder.clearCallingIdentity();
         try {
-            return runUsingImsManagerOrThrow(subId,
-                    manager -> manager.queryMmTelCapability(capability, regTech));
+            int slotId = getSlotIndexOrException(subId);
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            return ImsManager.getInstance(mApp, slotId).queryMmTelCapability(capability, regTech);
+        } catch (com.android.ims.ImsException e) {
+            Log.w(LOG_TAG, "IMS isCapable - service unavailable: " + e.getMessage());
+            return false;
         } catch (ImsException e) {
             Log.i(LOG_TAG, "isCapable: " + subId + " is inactive, returning false.");
             return false;
@@ -4232,19 +4243,28 @@
     public void isMmTelCapabilitySupported(int subId, IIntegerConsumer callback, int capability,
             int transportType) {
         enforceReadPrivilegedPermission("isMmTelCapabilitySupported");
+        if (!ImsManager.isImsSupportedOnDevice(mApp)) {
+            throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
+                    "IMS not available on device.");
+        }
         final long token = Binder.clearCallingIdentity();
         try {
-            runUsingImsManagerOrThrow(subId, (ImsFunction<Void>) manager -> {
-                manager.isSupported(capability, transportType, aBoolean -> {
-                    try {
-                        callback.accept((aBoolean == null) ? 0 : (aBoolean ? 1 : 0));
-                    } catch (RemoteException e) {
-                        Log.w(LOG_TAG, "isMmTelCapabilitySupported: remote caller is not "
-                                        + "running. Ignore");
-                    }
-                });
-                return null;
-            });
+            int slotId = getSlotIndex(subId);
+            if (slotId <= SubscriptionManager.INVALID_SIM_SLOT_INDEX) {
+                Log.w(LOG_TAG, "isMmTelCapabilitySupported: called with an inactive subscription '"
+                        + subId + "'");
+                throw new ServiceSpecificException(ImsException.CODE_ERROR_INVALID_SUBSCRIPTION);
+            }
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            ImsManager.getInstance(mApp, slotId).isSupported(capability,
+                    transportType, aBoolean -> {
+                        try {
+                            callback.accept((aBoolean == null) ? 0 : (aBoolean ? 1 : 0));
+                        } catch (RemoteException e) {
+                            Log.w(LOG_TAG, "isMmTelCapabilitySupported: remote caller is not "
+                                    + "running. Ignore");
+                        }
+                    });
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode());
         } finally {
@@ -4575,10 +4595,14 @@
 
         final long identity = Binder.clearCallingIdentity();
         try {
-            runUsingImsManagerOrThrow(subId, (ImsFunction<Void>) manager -> {
-                manager.addProvisioningCallbackForSubscription(callback, subId);
-                return null;
-            });
+            if (!isImsAvailableOnDevice()) {
+                throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
+                        "IMS not available on device.");
+            }
+            int slotId = getSlotIndexOrException(subId);
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            ImsManager.getInstance(mApp, slotId)
+                    .addProvisioningCallbackForSubscription(callback, subId);
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode());
         } finally {
@@ -4951,54 +4975,6 @@
         }
     }
 
-    //
-
-    /**
-     * Functional interface for encapsulating IMS related commands that should be sent to
-     * ImsManager for processing.
-     * @param <V> The return type
-     */
-    private interface ImsFunction<V> {
-        V call(ImsManager manager) throws Exception;
-    }
-
-    /**
-     * Run the specified command on the ImsManager for the subscription specified or throw an
-     * {@link ImsException} if the IMS is not available for any reason.
-     * @param subId The subscription to use
-     * @param func The function to run on the given ImsManager instance.
-     * @param <V> The return type of the function
-     * @return The result of the evaluated command
-     * @throws ImsException if the IMS service is not available for any reason.
-     */
-    private <V> V runUsingImsManagerOrThrow(int subId, ImsFunction<V> func) throws ImsException {
-        if (!ImsManager.isImsSupportedOnDevice(mApp)) {
-            throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
-                    "IMS not available on device.");
-        }
-        int slotId = getSlotIndexOrException(subId);
-        verifyImsMmTelConfiguredOrThrow(slotId);
-        ImsManager manager = ImsManager.getInstance(mApp, slotId);
-        if (manager.getSubId() != subId || !manager.isServiceReady()) {
-            Log.w(LOG_TAG, "getImsManagerForSubIdOrThrow: couldn't  resolve ImsManager, ready= "
-                    + manager.isServiceReady() + ", manager subId= " + manager.getSubId()
-                    + ", request subId= " + subId);
-            // if we have hit this point, getSlotIndexOrException has already checked that the subId
-            // is active for a phone, but ImsManager currently doesn't have the correct subId set or
-            // the ImsService has crashed/is not ready. The caller will have to wait for the service
-            // to be available before calling again.
-            throw new ImsException("The ImsService is not available for the subId specified.",
-                    ImsException.CODE_ERROR_SERVICE_UNAVAILABLE);
-        }
-        try {
-            return func.call(manager);
-        } catch (Exception e) {
-            // Some methods internally report RuntimeExceptions. Repackage those exceptions as well
-            // defined ImsExceptions.
-            throw new ImsException(e.getMessage(), ImsException.CODE_ERROR_SERVICE_UNAVAILABLE);
-        }
-    }
-
     private int getSlotIndexOrException(int subId) throws ImsException {
         int slotId = SubscriptionManager.getSlotIndex(subId);
         if (!SubscriptionManager.isValidSlotIndex(slotId)) {
@@ -5974,19 +5950,26 @@
     @Override
     public void getImsMmTelFeatureState(int subId, IIntegerConsumer callback) {
         enforceReadPrivilegedPermission("getImsMmTelFeatureState");
+        if (!ImsManager.isImsSupportedOnDevice(mApp)) {
+            throw new ServiceSpecificException(ImsException.CODE_ERROR_UNSUPPORTED_OPERATION,
+                    "IMS not available on device.");
+        }
         final long token = Binder.clearCallingIdentity();
         try {
-            runUsingImsManagerOrThrow(subId, (ImsFunction<Void>) manager -> {
-                manager.getImsServiceState(anInteger -> {
-                    try {
-                        callback.accept(anInteger == null
-                                ? ImsFeature.STATE_UNAVAILABLE : anInteger);
-                    } catch (RemoteException e) {
-                        Log.w(LOG_TAG, "getImsMmTelFeatureState: remote caller is no longer "
-                                + "running. Ignore");
-                    }
-                });
-                return null;
+            int slotId = getSlotIndex(subId);
+            if (slotId <= SubscriptionManager.INVALID_SIM_SLOT_INDEX) {
+                Log.w(LOG_TAG, "getImsMmTelFeatureState: called with an inactive subscription '"
+                        + subId + "'");
+                throw new ServiceSpecificException(ImsException.CODE_ERROR_INVALID_SUBSCRIPTION);
+            }
+            verifyImsMmTelConfiguredOrThrow(slotId);
+            ImsManager.getInstance(mApp, slotId).getImsServiceState(anInteger -> {
+                try {
+                    callback.accept(anInteger == null ? ImsFeature.STATE_UNAVAILABLE : anInteger);
+                } catch (RemoteException e) {
+                    Log.w(LOG_TAG, "getImsMmTelFeatureState: remote caller is no longer running. "
+                            + "Ignore");
+                }
             });
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode());