We get several calls a day from unknowns. It's gotten to the point where I'm blocking entire area codes, even my own. They use (spoof) our area code and exchange in hopes we will answer thinking it's a relative or neighbor. Ha, we don't have any friends, relatives, or acquaintances in our area code.
We started getting these unwanted calls in 2009, right after we moved here and got a new number. I added our number to the national DNC list, but it had no effect. The Do Not Call list is for legitimate businesses, and doesn't slow down the charities, debt collectors, political calls, or scammers.
In fact, I am convinced some of them use the DNC list as a source for legitimate numbers.