my only guess is student loans. I have one out and even though I am making payments I am not caught up and was told I will get calls until it is caught up. They send calls from every state I think to try and "trick" you in to answering. This is one of the numbers I get calls from regularly. So most likely AES or NCO.
Just FYI, AES would call from Pennsylvanie with a 7XX area code or only a toll free number since they are a legit institution. It appears to be some other third party. Hope it helps.