Planned Parenthood sounds right as they are the only group I've given to in the past year and they have often called me to ask for money without leaving messages. I don't answer unknown numbers, and this one has been calling quite a bit.
They called here tonight --- Donor Services --- I am on a 'do not call' list, but these idiots seem to find ways about honoring your wishes. Maybe blow a whistle into the receiver when a voice comes on - maybe THEN they'll get the hint (but they'd probably find a way to sue for a damaged eardrum)