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:
Another spammer that can't get their robo caller to work. About 5 seconds of silence and then a disconnect signal. A few clicks on my Panasonic phone and it is blocked.