I never pledge. If I want to give, I give a CC# over the phone. If I want to think about it, I ask to be sent an envelope. They always ask if they can put me down for $18. When I say no, they say they’re putting me down for $10, and I tell them no. They often later send me a bill. I know I didn’t pledge because it’s my policy (so that I don’t end up breaking a promise – tov shelo tidor…).
I would be dan these people l’kaf z’chus that nobody can really trust the recorded pledges since the telemarketers are often unscrupulous.
Although if they really did pledge, they obviously must pay.