We cannot be all things to all tzedakas. I give where I can, and will NEVER pledge on the phone any dollar amount. Just today alone I received 8 phone calls for separate tzedakas. I received two letters in the mail from the same mosad, addressed to the two of us as a couple, each with a different amount “pledged” and I do not pledge, I only say send me an envelope and I will see what I can do.
Don’t feel bad for nto giving. Just resolve to give generously when you can.