This is the Nature Conservancy folks looking for a donation.
They are a generally reputable non-profit environmental group.
(Three stars out of four possible on Charity Navigator.)
They called my number and asked for the former owner of my phone number by first name. He had been a past donor.
(I know he was the prior owner as I have had numerous calls for him and family in the year I have had the number.)
I explained, and they apologized and will remove the number from their list.
If they are calling you - they may be looking for someone that had the number quite a few years ago, as their records can be old. You can call them and ask to be removed.