Under the DNC law (Yes, I've read it.), prior to making their first call, a telemarketer must write it's own rules for avoiding calls to numbers on the Do Not Call List, and must have their company rules Approved by the FTC (Federal Trade Commission). They must also provide a copy of their company rules to anyone who requests it.
Generally these rules state that the company will subscribe to a monthly update to the Do Not Call List, purchasing a phone list which has been cleansed of numbers on the Do Not Call list. What Actually happens is that the cleansed list costs more than the generic list that includes All numbers, so they quickly slide into buying the cheaper list that includes the DNC numbers.
Interestingly, this could well be construed as a violation of their own rules, since they probably agreed to purchase the cleansed list. Under the law, if one can prove that they are violating their own rules, they can be found liable for treble damages in a court of law, usually small claims court. The standard price that can be collected on an illegally placed telemarketing call is $500. Treble damages means that they could be obligated to pay you $1500 per call.
I gave up on reporting numbers too ... I was doing it a couple times a week. .. put myself on do not call list every month ... Unfortunately it's useless...
Once you put your number on the list, its there until you remove it. By re-doing this monthly, you have opened yourself up to legitimate business's for another 30 day's therefore effectively messing up what you have put your name on the list for to begin with. Still, the DNC is not a call blocking device and the criminals will continue to call despite any law.