I have a Gigaset phone and it offers the option to cancel the ring when the callerID is blocked. It may stop some people reaching me but at least it does not annoy.
I also use drunk glaswegian on them if they happen to reach me. The alternative is to do the pervert. "What are you wearing, do you like people linking your toes" etc etc.
I once let them get all the way through (double glazing conservatory sales) and then asked them if they were able to fit the conservatory. I was in flat 3 on the second floor. It took them a moment to work it out and then got quite angry.
