Who called from 3018829983

I KEEP GETTING CALLS FROM CMC AND NO ONE IS THERE.  THE CALLS COME IN SOMETIMES MORE THAN ONCE A DAY.  WHAT CAN I DO?

They call and do not leave a message.  The caller ID says CMC.

this numbers shows up on my caller ID several times a day. I registered my number on the "do not call list". I think they get around this by calling themselves a charity. The caller ID says CMC. Nuisance calls

Please close the account CMC 301-882-9983!
Apparently, this is an automated call service that calls at all times of day and night.  They don't leave a message.  Truly bothersome!  Who are they?  How are they getting this number?  Why do they call?