Service dies even I created separate thread to the broadcast receiver which is inside the service

Question

I'm creating an App to monitoring call logs and send them to the cloud(Firebase Realtime database). I created Service to alive the app. Inside the service class, I created a Broadcast receiver to monitor the phone call states. I know about the background service restriction in android oreo and above

1. First, I register the broadcast receiver like this

   @Override
    public void onCreate() {
        super.onCreate();
   
       IntentFilter filter = new IntentFilter();
       filter.addAction(android.telephony.TelephonyManager.ACTION_PHONE_STATE_CHANGED);
   
       registerReceiver(receiver, filter);
   
    }
   

After that, I can able to see call state changes as toast messages. but I try to save to the firebase realtime database inside the phone state listener class, My app background service stops. So I register the Broadcast receiver with a separate thread like below

@Override
   public void onCreate() {
      super.onCreate();

    IntentFilter filter = new IntentFilter();
    filter.addAction(android.telephony.TelephonyManager.ACTION_PHONE_STATE_CHANGED);

    HandlerThread handlerThread = new HandlerThread("ht");
    handlerThread.start();
    Looper looper = handlerThread.getLooper();
    Handler handler = new Handler(looper);
    registerReceiver(receiver, filter, null, handler);

}

Even though My background service stops. What went wrong here?