It's Oregon DHS offices in Portland. The "jail" story is a standard lie so that "services" like WIC don't have to explain why they won't identify themselves. The number gets moved around occasionally, but is always DHS. I got lucky and talked the guy on the other end up to find something out, after getting my sixth in a row, and while I was on the phone I heard a co-worker give her number out to someone. I did a reverse trace on it, which turned out to be a private cell, called and asked who the guy was sitting next to her. Went to the address, and got a match with the voice and a real person. It turned out to be a John Davis that works in DHS IT by the Lloyd Center. Don't know what the scam is, he would only say he worked on "Rusty Coathanger", which turned out to be the state abortions database. It's in MS-Access! Figures! In a country run by fraud, IT is the biggest...
As to why they call you... Seems to be a case of the collection agency that just doesn't understand someone moved/thinks everyone is lying scenario. They are checking on Food Stamp or WIC recipients who have moved without updating the number. They've seen something suspicious in the data and are calling on a fishing expedition. My advice is to have some fun with them. They seem butt stupid. Feed 'em some data and waste their time like they're wasting your.
You pay for this and call it a service? Real "progressive", Oregon...