Correct, the mystery charity never needs to scrub the DNC registry. For Donor Services it's a different story. As a commercial fundraiser, DSG is expected to honor an internal no-call list and add any number upon request. Break that order, the FTC declares, and ''the telemarketer may be subject to a fine of up to $16,000.'' They are also covered to a point by other regulations for telepests, so you can kvetch about abandoned calls, bot calls to mobile phones, and so on.
Linked below find the simple steps I took to rid myself of a competing major pain charity beggar by politely rubbing its face in federal laws. You will note that I never rely on verbal cease-communication demands.