The Do Not Call List or DNC means nothing to scammers! Only honest people will use it, anyone else you can surmise is a scammer trying to drain your wallet of money!
That was a robocall, a machine calling randomly. When you answered, it recorded your number as a live number. Now you will get calls from real people trying to scam you. Next time don't be so quick to answer. Beware "service calls" and any number you don't recognize. Don't pick up. If they persist, block the number. Just trying to help!