Like Damian, I also have a Truecall unit, and this may read like an advertisement, but it is my own experience of this product and as the subject has come up, I feel its worth pointing out how effective Truecall has been for me and my wife.
Before I got a Truecall unit we were frequently receiving 4 or more scam/ unwanted advertising / ambulance chasing calls a day and the worst are silent calls from automated dialers. This was not just annoying, but becasue my wife has mobility issues it was actually causing her unnecessary pain to reach the phone if I was not at home to pick it up.
SInce having Truecall, not only do we get disturbed far less, far fewer unwanted calls get through I'd guess about 1 every two months or so and only from callers who are real people, which is a massive and welcome reduction.
The system is really very clever, and it offers several different ways it can be used. Initially it may take a little time to set it up , but once its done it works almost seamlessly, and so far with total reliability for me.
I also use Trucalls web based support service (with subscription fees) This extends the monitoring of the Trucall device, and allows me to check what numbers have actually called me, and how they were handled. This has proven very useful on a number of occasions.
If you receive a call from a number on your "Zap list" the unit intercepts the call and tells them not to call again and cuts them off - without my phone ringing at all. Ahh Bliss.
There are of course other systems that claim to offer some of the fame functionality but according to Which? magazine the Trucall unit was was the most effective of the bunch.
I would heartily recommend it, and suggest it would be a great system to get for elderly relatives who may be considered vulnerable to phone scams.
As for forgiving people who need a job and take on call centre opportunities, I have no sympathy for them when they must realise that what they are doing is a scam, or cold calling.