Spammer. They called after 8:30 pm, left no message. I tried to call back and was hung up on before I could speak. I called again and got a message saying it's the "Center for Research, and no agents are available right now." I received this on a cell phone, that is on the do not call list. I reported it to the FCC via the do not call webform, and will contact ATT and SNET to report them tomorrow morning.
If they call, make sure you report them to the FCC as well. It's not a collections agency. I would recommend not even answering, as you'll likely just get a fake automated recording of some kind.