How do you stop getting calls for donations?

In the United States, go to the Do Not Call registry at the link below and register your phone numbers. This should eliminate most private businesses from calling you. (Political parties are not covered by this, darn the bad luck!)

Then, whenever you get a phone call, inform the caller that you are on the Do Not Call registry, and ask them to remove your name from their list.

Another thing you can do is to ask the caller what percentage of your donation actually goes to the charity, and what percentage goes for fundraising expenses. Many of the call centers keep from 80-90% of the money raised, sending only token amounts to the charity. When they tell you (and in the USA, they are REQUIRED to tell you) how much of the donation actually goes to the charity, tell the caller "You should be ashamed of yourself!".

They generally won't bother you after that.