Missed call at 5:19 PM. No message left. No name on caller ID

Got a call from this No., they left no mssg.  I think they are looking for someone to scam

called approx 5:30pm may 25.  no message

Have received a call every day for about the last week from Maritz Research 636-200-0115.  Today went on line typed in Maritz.com, got a toll free contact # 1-877-462-7489.  A "live" person answered and after getting their name requested that my # be put on the "do not call" list.  Was told it would be done but might take a couple of days.  I do not take calls of this nature and was tired of the annoyance.

I answered this unfamiliar number and it was silent for about 7 seconds then they hung up. wierd!