Your question is confusing because, if we are talking about your federal tax refund, only the Bureau of Fiscal Services can collect a debt or process an offset. It might have been requested by another collections agency, I suppose. But if you haven't talked to the BFS, I would call them first.
https://www.irs.gov/taxtopics/tc203
The BFS can collect any federal debt, including tax debts and debts relating to other federal contracts, as well as child support and unemployment compensation (if you owe repayment). AAFES does appear to be a federal debt that would be eligible for offset.
The Exchange Credit Program (ECP) is administered by the Army and Air Force Exchange Service, a nonappropriated fund entity of the Department of Defense. Established by Congress in 1979 to protect service members from predatory lending, the program offers responsible credit solutions to Warfighters and their families.
You may want to do some research into the Military Lending Act.
https://files.consumerfinance.gov/f/documents/cfpb_military-lending-act-know-your-rights_handout.pdf
https://www.fdic.gov/resources/supervision-and-examinations/consumer-compliance-examination-manual/d...
There does not appear to be a statute of limitations on debt collections built in to the MLA; if there is one that applies to you, it would be in the state where you were a resident when you had this debt.
https://www.consumerfinance.gov/ask-cfpb/what-is-a-statute-of-limitations-on-a-debt-en-1389/
You would probably have to start by contacting the consumer finance protection agency in the state where you live, and/or the state where you lived when you had the credit card.
