For 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, not just to the DNC alone:
For text messages: forwarding any text message spam you get to the short code “7726,” which spells “spam” on most phones, to alert your network operator to the abuse.
By State DNC lists:
http://800notes.com/res/DoNotCall.aspx
I had Mr Number on my old phone after I started receiving calls from outside the United States and found it came in handy. But I really do not have experience with latest version. With that said, look into the apps available and find one that fits your needs.