I have set up an email address a long time ago that I use for all organizations/businesses that I believe most likely sell or let other companies use to contact me. I keep the one for important people/business separate which means a little less spam.
I know that some of these companies or magazines make a little revenue off of these sales. So what. I know what is spam or not and it is easy to delete, usually takes about 10 seconds. Why spend time complaining to somebody that may or may not have done something. In your case they have not responded as of your last post I assume. Are they guilty?? Will you stopped being a member? How much time have you spend and gotten upset over it?
If you like the organization then you going to have to accept their business practice, if not leave but they already have your info.
Also nowadays good luck with your information not being shared with another company. Your CC company does it, bank, you name it. I expect it and use the check mark and delete button.
And I am not tying to be snoody, just my two cents and the way I handle it.
I would add that I work in the government and for some odd reason we get spam there also, and we use our emails only between agency's. I have never given it to anybody. Nothing like a spam alert from the IT Dep. " Improve your size" that your IT department is asking you if you would like to accept this email.