The way their process worked was:
* Big company wanted a survey completed. * Big company would want it targeted to a specific state/regional area, so would provide a list of post/zip codes.
* Survey company would translate the list of codes into phone prefixes for each area.
* Computer would randomly generate phone numbers in the area - starting from xxxx 0000 through to xxxx 9999 for operators to call.
That meant you'd get disconnected numbers, businesses, private/silent numbers, faxes, modems, etc.
So having a "clean" number didn't protect you. While a few projects were targeted to specific people/numbers - most were just random.