This is an on-going scam that changes phone numbers -- they are debt collectors posing as an government type legal agency. If they harass you at work, report them.
This number is associated with 404-692-7756. That number has alot of comments regarding scam. Just a heads up on a new number being used for this crap!
ID themselves as "Premier Investigative (Mumble) Services". No other information was given, but it seems clear this is some sort of debt collection scamming operation.