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.
For Extortion Scam Operations, File reports with the FBI, your state attorney general and Department Of Justice,CFB,FTC & FCC..
http://www.nw3c.org/
http://www.ic3.gov/default.aspx
http://www.fbi.gov/
https://www.ftccomplaintassistant.gov/#&panel1-1
https://esupport.fcc.gov/ccmsforms/form1088.action
http://www.consumerfinance.gov/complaint/
http://www.fraud.org/
http://www.stopfraud.gov/report.html
Tip off FBI about this extortion attempt by filing form at: stips.fbi.gov/
Also see here:
http://800notes.com/arts/I2neMkbUAAo/where-to-report-phone-crime