The problem is that charities can still call you (albiet within certain hours).
We get far more calls from charities than telemarketers. My suggestion is, never give to a charity that calls you up because they just keep calling you back.
Just so everyone doesn't think we don't give to charities, we do, just not to those that call us up. We give to those that quietly take my money away each month without me doing anything and without interupting my dinner.