Me too. I have been getting a lot of calls from this number recently. I never answered and they never left messages so I finally called them back. The person at call center confirmed that they were calling on behalf of the Natural Trust for Historic Preservation. The person was very polite and agreed to take my number off the call list.
I *was* a member of the Natl. Trust. I still believe they do great things, but I know that harassing people with multiple unsolicited calls is a *great* way to erase any good feeling associated with the organization. They've called our household about eight times in the last three weeks, and would NOT leave a message when asked by one of us.
If you are contemplating membership, please do NOT give the National Trust your phone number.