billing on closed account

I closed my account in August 2022 as I moved to another country.  In August of 2023 I received a bill from a collection agency for the amount of $831 which I reluctently paid.  I just received another bill for $277.04 and when I talked to customers Service I was told that it was the remaining balance.  I told her that the account was closed in August 2022 and asked why I was still being billed on a “CLOSED” account.  The representative could not give me an answer and asked that I contact the collection agency that sent me the bill.  I tried contacting the store where I had opened and closed the account and they said I would have to come in to their store with a validation ID before they can look at the billing statement.  That’s hard to do since I’m no longer in the U.S.  I need answers!