I don't know this series, but back in the days while still living in a big city, we had quite a lot of unsolicited sexually harassment calls, even when the kids answered the phone.
So blowing the whistle attached to the phone was the only way to send them packing and never try again. Nasty...
Using a whistle gave me peace. Years ago, I had one fixed to the landline phone for quite some time to welcome this kind of callers and it worked like a charm. 😇