Charities and telemarketing companies must each maintain their own DNC list. While charity calls are excempt from the national DNC list, if the calls are being done by a telemarketing firm they have to checked against both the charity’s list and the telemarketer’s list. If you are called and you want them to put you on their DNC list you need to specify which list or both lists.
This only applies to calls made by a telemarketer, if the charity is calling directly they do not need to maintain a DNC list.