NBPI - USSA ripoff Annoying never let up! Las Vegas Nevada

I'm tired of recieving these fraudulent letters claiming i have won over 3 million dollars and then they have the nerve to ask for money lol... they never give up. I'll recieve the letter one month and not respond to it and so i figure its over but its never over a few months later i recieve another letter stateing that if i dont respond with in so many days I will loose out on this so called prize but then a month later there is another letter saying the same thing... they just dont give up. How do I make them stop?

Amber
Anchorage, Alaska
U.S.A.