Disable Wi-Fi Calling when getting "registration error" intent.

        @Override

        public void onReceive(Context context, Intent intent) {

            String action = intent.getAction();

            if (action.equals(ImsPhone.REGISTRATION_ERROR)) {

            if (action.equals(ImsManager.ACTION_IMS_REGISTRATION_ERROR)) {

                // If this fragment is active then we are immediately

                // showing alert on screen. There is no need to add

                // notification in this case.

                // not show notification, we are changing result code here.

                setResultCode(Activity.RESULT_CANCELED);

                // UX requirement is to disable WFC in case of "permanent" registration failures.

                mSwitch.setChecked(false);

                showAlert(intent);

            }

        }

        mButtonWfcMode.setOnPreferenceChangeListener(this);

        mIntentFilter = new IntentFilter();

        mIntentFilter.addAction(ImsPhone.REGISTRATION_ERROR);

        mIntentFilter.addAction(ImsManager.ACTION_IMS_REGISTRATION_ERROR);

    }

    @Override