GC Services is one of the oldest debt collection agencies around, the home office is in texas, though there are many locations in michigan, phoenix, etc. These guys are pros, they know the law and will sometimes break it, mainly by disregarding state laws which prohibit disclosing the nature of the call to relatives or roomates, and sometimes spouses. Knowing how embarrassing it is to have people calling you for past due bills, which they admit their clients (american express, mainly) have insurance policies that cover these unpaid bills. Tactics include using switchboard.com to find your neighbors phone number and asking them to leave a note on your door, because you wont pick up the phone.

who is this caller