CID was Denver CO.  Caller did not leave a message.  Caller has been blocked

Sounds like a computer impersonating a human calling from the Pro-Life Committee which is a project of the National Campaign PAC, a federal political action campaign. FEC ID is C00563759, so google that to learn more.

I found a solution to this problem. They usually call me only once. Most of these calls are being generated by a computer. There is something called Special Information Tones or SIT code, which the phone company plays to identify a non-working number.  They are played just before a voice recording saying, "Beep Beep Beep (the beeps are the SIT tone) the number you have dialed is no longer in service..." When automatic dialer hears the SIT tone, it hangs up and takes your phone number off their list. I Googled SIT code wav and found one. Downloaded it and rerecorded my answering machine greeting placing the SIT tone in front of my greeting. I used to get a dozen calls a day from telemarketers.  Within a week of playing these notes on my answering machine message, I get maybe one!

These parasites called twice today.   My block list caught it and dealt with them.

Caller ID says: Contact Center,     they were blocked but still call up to 4 times a day