Ahem....scamers and trollers do not care about the Do Not Call List - they are criminals. Stop answering you phone every time it rings - particularly if you don't recognize it. Come here first and check. Then call them back.
Just now got this call - and like I always do call it back from work land line. Bingo! I got a computerized voice saying "the number you have dialed is unallocated." This tells you that it's a scammer. People please do not answer a number you do not recognize.
Iris! Stop answering your phone every time it rings! Try to resist. Once they get a warm body on the other end they will never leave you alone. Block the number! It's that simple.