Most numbers are spoofed. The illegal callers in no way want you to know what and who they really are since they can get into mega trouble for the tactics and loads of fines over breaking the laws. Even the ones in foreign country's don't want you to know who and where they are and use call spoofing to hide where the call is originating from.
phone spoofing explanation
http://en.wikipedia.org/wiki/Spoofing_attack
http://www.fcc.gov/guides/caller-id-and-spoofing
Consider maybe getting a call blocking device or phone.. You can google them and many are around $50.00 or so.
Report your callers here, not just to the DNC alone:
https://www.ftccomplaintassistant.gov/#&panel1-1
https://esupport.fcc.gov/ccmsforms/form1088.action
https://complaints.donotcall.gov/complaint/complaintcheck.aspx?panel=2
By State DNC lists:
http://800notes.com/res/DoNotCall.aspx
FCC Abandoned Calls Complaint form:
http://www.fcc.gov/cgb/consumerfacts/1088D-R.pdf
email:
[email protected]