I know where you're coming from. I get a lot of unsolicited calls and they're definitely annoying. Like what you do, I let the answering machine take anonymous calls. At other times, when I'm not too busy, I pull pranks on them. And it always makes me feel good when the callers become frustrated after they realized I have wasted their precious time. 99% of the time, they never call back. I find these pranks more effective than being on the DNC list.