Dec. 19, 2016, 2:12 PM - missed call from "301-360-0350, Maryland" to my cell number that is on the national DNC list. I got up to answer, and as I entered the kitchen, the phone stopped ringing, and it appears on my cell call log as a missed call. I called back the number on Caller ID right away - it was still 2:12 PM - but got a busy signal.
Consider a call blocker instead of relying on the DNC to stop these scam calls. Also calling these numbers back can verify your phone number and result in more scam calls. Try ignoring and blocking scammers instead, it does cut back on these calls with some patience.