It's probably not the actual organization that you're talking to. The Nature Conservancy likely hires a third party solicitation company to do fundraising. If you report your complaint directly to TNC, via their website or a call to them directly, you'd probably A) get yourself removed from the calling list, and B) alert them that the fundraising company they've hired is doing a very poor job and is driving away potential donors. There are a lot of companies out there that TNC can choose from for fundraising and if donors are complaining about the work by this one then TNC would be very incentivized to find one that does a better job.
Called (800) 628-6860, listened a bit, pressed 5, they looked me up by last name & zip (so it was a targeted call) had them place me on their “inactive” or DNC list. I'm blocking their number anyway.
Have received one or two calls from "TNC", as it appears on the caller ID, with the number 661-670-2568. I usually screen incoming calls, via my answering machine, if I don't recognize the incoming call ID. Usually, the caller hangs up before my answering machine kicks in. This would indicate to me the call was for telemarketing purposes, or a legitimate wrong number call. This "TNC" may be a spoofed call, as reportedly the area code does not represent The Nature Conservancy main number. Not sure. I did recently contribute to The Nature Conservancy, so the call's might be legit. However, I have already donated, so this number in question goes on the reject list, advising the incoming caller - on the FIRST ring - "You are not authorized to call this number", followed my a disconnect. The reject system also keeps tab on the number of times a call has been received from a "rejected" number.