File complaints with your phone service provider and local LE.
Consider getting a call blocking device or phone.. You can google them and many are around $50.00 or so. 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.