For Cold-calls

One very effective way to turn away cold-calls is to left the phone and ignore completely.
The person will cut off the call as soon as he/she notices there is no one to response on the other side. I always use this way to turn away those cold-calls. This is the very rude way, but the rudeness is, I assume, the same as the cold calls themselves.
...Oh, but even they are rude, it's a good act to be kind to them. So, how about playing a CD in front of the phone? It might be better than just ignore. Don't you think? I'll try this in the next time!