I used to work in telemarketing.....
The thing they usually fail to mention about the "do not call lists" is that list is usually catered only to that specific company. So, just because you asked one phone marketing company to put you on the do not call list, does not mean your number is not still floating around to other phone marketing companies, and other huge telemarketing number lists.
For you to officially be on ALL the do not call lists world wide, takes a LONG time.