I don't pick up on calls that don't have a legitimate Caller ID (and even if they do, I also don't pick up if I don't recognize the caller). I subsequently blocked the number.
Fax call to our land line from 720 606 7106 woke us up at 6AM. It is from a company called NetProwa (http://www.netprowa.com/) which seems to be making calls at random to drum up business for getting phone numbers taking off companies' call lists???!!. We filed a complaint with the FCC (http://www.fcc.gov/complaints) but don't know what good that will do. Maybe if enough people file a complaint the FCC will get off their a-- and do something about companies like NetProwa.