We had an annoying one come to the door once and he wouldn't take no for an answer.
He wanted our bank details to give a donation, I'm sorry but I don't think so. I don't give private details willy nilly to strangers.
DH offered him £1 cash but funnily enough he wouldn't accept.
If I want to donate I will do so with the charity not some dodgy looking bloke at my door.
Sorry but I'm very sceptical about these things, like when you get utility people trying to get you to change to them I just say "sorry not interested" and shut the door.
Firm but polite lol.
Never feel guilty
Cx