They do not need to call my home after 9:00 at night. I find it hard to be nice to the "student" who: wakes my children three nights in a row with a post 9:30 pm phone call and who tells me that because they are a non-profit they can call my home at whatever time they choose.
Furthermore, I gave my annual donation already and don't appreciate repeated phone calls asking for more money.
I never pick up for any 'charity' call.
I don't think they would respect a request to be taken off their list.
When a robo dialer calls several numbers at once the person only picks up the call that has been answered - so that is why often there is dead air. All other numbers are dropped.
As far as I am concerned if a charity wants money, from a credit card or otherwise they are phishing.