At first I believed this was a scam number because caller ID had 7734094803 (which I checked via 800notes post comments stated scam) requesting me to call back to the 8667497279 with no info for why I should call back (still haven't).
After reading all post for the 866 number, I recalled receiving a letter from GC Services Limited Partnership (it was in Dec) which I ignored because I was making payments via IDR (state taxes) website.
I retrieved the letter which included the phone number 8667497279 but not the 7734094803. They started calling in Feb 2016...WOW! I will continue payments via IDR website, totally ignoring third party GC Services.
Not a scam number!
Third party collection agency.