You need to identify who exactly your lender was. If Citizens was your lender, and AES was only a servicer, you can disregard AES (as instructed by Citizens).
However, if AES is your lender, you need to work with them.
It is incredibly important that you keep all of these communications in writing, use "confirmation letters" - see my note below - when communicating by phone.
You can make an argument that you are entitled to a return of the money you paid, but the creditor is unlikely to return it. (They wouldn't have an obligation to do so).
Unfortunately it appears that there is a significant amount of confusion over the status of your loan following the bankruptcy and you need to straighten this out (again, in writing) to confirm your liability (or lack thereof - hopefully your conversation with Citizens was correct), and you can then move forward from there. If your loan status had been confirmed at the time of your bankruptcy discharge, that would have been the time to dispute any future payments to AES, as opposed to making a request for return now. (Again, it is perfectly acceptable to make a request for reimbursement, but not possible to require it).