I called the number to see who answered. The recording said it was the Donor Care Center, claiming to have called on behalf of the Humane Society. I don't trust this "Donor Care Center"...I've never received a phone call from the HSMO for fundraising. HSMO's campaigns include direct mail, not phone calls. This "Donor" place sounds like a sham organization to me.
I get a call at least every day. I don't answer, and they don't leave a message - other than waiting long enough so I get a dial tone on my answering machine.