I went through that when I was a member of 'Friends of the Earth' many years back. They were the only organization I'd given my name/address to. About three weeks later I was hearing from every f'ing organization on the planet. I phoned their head office and of course they knew nothing about any of it. I ended my monthly contribution and sent a scathing letter to the head office and informed them that if they didn't get my name back from the other organizations I would show up someday and take a baseball bat to their office furniture then wait to be arrested so as to get some newspaper interest in the story. One organization I know of that honours their commitment to silencio regarding yer info is the War Amps. Great group that does good work.