Many of the telephone solicitors tell me that I gave a certain amount in the past and ask that I repeat the contribution. The problem is that I never heard of that organization before and never gave them any contribution. I give regularly to a couple dozen tzdakas that I know although I receive solicitations from over 150 different ones during a year.
I assume that the telephone solicitors, who call us several times a week get a percentage of the supposed pledged amount.