Telemarketer Nightmare

I have a multiple phone number line at home. The main number is actually not used at all and is muted. The advantage of that is that should a phone company ever illegally sell data, the buyer would always end up with that number that's never answered. However, it happens that sometimes there is a call on the display. Now, normally Telemarketers call with "number hidden". But unfortunately they cannot do that with me. I have a function, where if somebody calls with a hidden caller ID, my phone simply generates a message "this connection does not accept calls with hidden caller ID". So either the guys give up or they reveal themselves. If they do reveal themselves I can then check, if the number is in the directory. Recently there was a Telemarketing company being extremely patient and I had their number on the display once a day for about two weeks. They would even call at times like 9 o'clock in the evening. So I got angry and did the following: I deviated the phone line they called to their own number :-D Funny enough, their phone terror stopped immediately...