Duct cleaning service.  Most likely a scam, as we are on the national do not call list AND our house is less than a year old.  NO company name provided.  They have called our house three times in less than a week. Asked them to stop calling and remove us from their call list the FIRST time they called.  Apparently that hasn't happened.  The person on the other end of the line each time is male, accent sounds of Indian origin.