Charities, along with some Survey's and Political calls, are exempt from the DNC, however, they can still get into trouble for not placing you on a internal DNC when asked, you can also check your states laws in regards. Some states have different laws in regards to the calls, which can differ from the federal but as far as I know, Oregon is the only one that does not allow Charity calls.
Do consider maybe getting a call blocking device or phone.. You can google them and many are around $40.00 or less. If its a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number.
Report your callers here if they continue to call and harass:
Customer survey concerning voter registration. They said it might take 18 minutes but after they found out I was white their quote was filled and the call ended. Do not know the true nature of the call.
Introduced himself as David Marsh from a political, national research company. I politely stated that I did not have time to answer questions, wished them a good day and hung up.