Do Not Call

I originally signed on to the ‘Do Not Call’ list some years ago, and it has been a total success as far as I’m concerned. It took about a month, and my phone went silent. No more annoying sales calls at dinner time, no more annoying calls, ever.
My question. How do the people who make these calls know you are on the list?

Source: National Do Not Call Registry

In real terms, it means that IT has to build a database interface with the call center software and cross-reference it with the do not call file. It isn’t especially difficult but it is expensive and time-consuming and the stakes are high. Modern call center software is pretty sophisticated. It blasts a bunch of calls out to a population and then passes off the ones that are answered by a person to a bank of telemarketer operators that are standing by to take a call. Matching calls to operators happens very quickly and dynamically to make things as cheap and efficient as possible.

The Do Not Call file just adds a step in which the numbers on the list do not get called by the system. There are still some smaller operations around that do things by hand. I have no idea how they comply.