Such callers, even the robots, enjoy listening to Radio 4 Extra or the net feed of the Goon Show when I put them on hold as I "transfer" them to our "IT dept". If I have a spare minute I like to discuss philosophy with them instead, or sell them double glazing as the fancy takes me
Then the numbers get blocked using the BT service, as BT can see the real number behind the spoofed one that I see perhaps something can be done to block before it gets to subscribers. I have seen a marked reduction in the past 6 months so it maybe so.
BT Infinity 2, HG612, Billion 7800N; 79987/19999 Kbps. Online since 1987. Macs since 1979. Dreambox fun. Advanced Radio Amateur Licence and an anorak.