Quote:
I really wish I could find a way to block calls presented as "Unavailable" to my UK ntl line. I've got number withheld blocking, but international telesales still get through

That is the main flaw, and unavailable can be presented by other methods too - eg. "SS7" capable exchanges which are directly connected to the network.

One idea is to screen calls through a bit of software and a Caller-ID capable modem. Because the ID is sent before the first ring I think they can pick up the phone before you hear it, and play a message or just drop the line.

Possibly Asterisk could do all this - I haven't looked into it but it is worth a look.

Gareth