If you call back and the message tell you it isn't a working number there is 2 things you need to know.
Firstly, it is a working number but cannot receive calls hence the non working number. Secondly, they may be piggybacking off some else telephone line which is highly illegal. The Federal DO Not Call List is a joke. The only good it does if the case goes to court the prosecution can use it to get a federal indictment.
Got a call from this number today, claiming to be Publishers Clearing House, telling I was the in the top finalist, immediately thought this was a scam, but I give them a chance until they asked for my credit card number, I truly hung up the phone very quickly.
I got the call lady said she's a senior account exec and I'm eligible for $1 million and wanted me to verify my first and last name. Pretty sure if you said my name when you called you should already know my name. Told her wasn't giving out info over the phone. She said hope all goes well with you have a good day and hung up. Then I blocked the number.