alan_m wrote :
Try just blocking International and number withheld first and see how many
calls stop. I've found with just these two filters 100% of unwelcome have
been stopped in a period at over 3 months.

This will allow your warning calls through as long as they present a number.
If they don't present a number then you have no way of filtering them to a
white list in any case.

Bank and credit card fraud departments will not reveal from which number they
will call you as its easy for the criminals to spoof a calling number.

We had Talktalk's call filter enabled a couple of years ago, which
allowed us to blacklist many of them, including those who withheld
their numbers. It initially worked well, to bring the calls down from
10 per day to close to none over weeks.

Now they seem to spoof numbers, or even local numbers to get through,
so I bought a quad set of BT8500's. I have this set up to block all
anonymous callers, all international, all begining 00, but everyone in
the call book gets straight through. I was being pestered by spoofed
020 area codes.

If someone rings and presents a number and is a human, they can
indicate who they are with their name, then press #. The phone then
rings, plays back the name and show the number, I can then decide what
to do with the call.

It has so far filtered out 4 nuisance callers, but the pre-recorded
calls from utilities I mentioned in my OP, will not get through unless
I can find a way manually add their numbers to the approved list.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk