How to call setCoordinates(int lat, int long) from within MainActivity?

// some methods omitted
public class MainActivity extends Activity {
    Boolean isBound = false;
    Messenger mServiceMessenger;
    Messenger mActivityMessenger = new Messenger(new ActivityHandler());

    ServiceConnection mServiceConnection = new ServiceConnection() {
      @Override  
      public void onServiceConnected(ComponentName name, IBinder binder) {
        isBound = true;
        mServiceMessenger = new Messenger(binder);
        Message message = Message.obtain();
        message.replyTo = mActivityMessenger;
        mServiceMessenger.send(message);
      }

      @Override
      public void onServiceDisconnected(ComponentName name) {
        isBound = false;
      }
    };
    class ActivityHandler extends Handler {
      @Override
      public void handleMessage(Message msg) {

      }    
    }
}

public class GeolocationService extends Service {
    int mLatitude;
    int mLongitude;
    Messenger mMessenger = new Messenger(new LocationHandler());

    @Override
    public IBinder onBind(Intent intent) {
      return mMessenger.getBinder();
    }
    void setCoordinates(int lat, int longitude) {
        mLatitude = lat;
        mLongitude = longitude;
    }

   class LocationHandler extends Handler {
      @Override
      public void handleMessage(Message msg) {
          mLatitude = getLatitude();
          mLongitude = getLongitude();
          Message message = Message.obtain();
          message.arg1 = mLatitude;
          message.arg2 = mLongitude;
          msg.replyTo.send(message);
          setCoordinates(mLatitude, mLongitude);
      }
   }

}

  public class Difficulty {
    public static Boolean HARDMODE = false;    
  }