Unless you specifically say, no selling of data, I think they feel its ok to make "extra" funds out of one donation.
My elderly father, who does not believe in donations, never donated to the Salvation Army.
I have for a long time, my dad had purchased things from the likes of Magnamail, and got a plea letter from the Salvos.
I have in about 5 years now, now, told them several times, that I am not ever increasing my amount to you, ie, Salvos, because you used the money I donated to buy data.
Aust charities I don't know why, but all of the authorising authorities in relation to charities and privacy, don't feel there is a need to tighten the buying and selling.
I even contacted the ACNC and they said, o, its not a part of their remit to narrow down the buying and selling of data, contact the consumer affairs commission in your state, bah humbug.
From a while back, when I get a "gift" from a charity, I write a terse letter.
You can tell from the envelope, a CM (charity mail envelope), from Strawberry Hills NSW will be it.
Just return to sender, not at this address anymore, might work.
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Send a letter to the 12 charities and explain how you feel.
They might take you off their list.
If you keep quiet, they will keep sending said gifts, or even sell you data to the 1500 other Aust charities that are unscrupulous in this respect/regard, ie, buying and selling of data.
Yes, its $1.20 per envelope, $15 tops, but otherwise you will be "bombarded".