Oh, right you have to say some MAGIC WORDS LOL.Idiot!
Much simpler solution. Get a whistle, and when one of these subhumans comes on the line, blast away.
You may have to repeat, there are very few neurons on the other end of these calls, but nothing says STOP CALLING FOREVER like the whistle. Airhorns work too.
It's not like they are asking for money or trying to sell you anything. Blood supply shortages are a serious issue. I pray to God you never have an accident or illness require blood transfusions. You don't deserve them with that attitude. And simply saying "never call again" WILL stop the calls.
It only bothers you when these "subhumans" call you because it makes you feel bad to say no. If you are going to say no, I just wouldn't answer, or I would do what was suggested earlier and ask to be put on their do not call list. When you get on the phone and talk about how their locations aren't convenient, or you are just too busy to donate...or whatever lousy excuse it is that you have, you are only wasting your time as well as theirs.