Its called call spoofing, that is how. This is hard to track for the feds to be able to deal with also!
phone spoofing explanation
http://en.wikipedia.org/wiki/Spoofing_attack
http://www.fcc.gov/guides/caller-id-and-spoofing
*****************
There is a way to deal with this. 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.
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]
To file complaints on Foreign company's:
eConsumer.gov: Report Your Complaint
E-mail:
[email protected]