The Telecrapper 2000
I remember back when I had an ISDN line. I used our computer as an answering machine and had the possibility to make personalized messages depending on the number of the caller.
For the people calling from an "empty" number, i.e. telemarketers, I routed them directly to the answering machine and simply said "Based on the number you are calling from it seems like you are a telemarketer. Please leave a message and I will call you back". The only messages I got was some mumbling about "what is this?" etc..
Now, welcome the Telecrapper 2000. Record a series of short audio ...