Santander Bank US Bank Account Or Service Complaint

Santander Bank US Bank account or service department,

Other bank product/service Account opening, closing, or management Michigan

We had a line of credit loan with Sovereign Bank. Santander Bank apparently acquired the rights to this loan. After getting the run around with Santander, we paid the loan off in full with Santander in - 2013. Yesterday in the mail, I received a bill for $65.00 from Santander for a fee on this account. I called Santander. I was passed around to four different operators. I asked to speak with a supervisor after speaking with the second operator. I was never handed off to a supervisor. I was told I needed to go to a local Santander Bank branch to prove my identity. Yet they kept verifying my identity with each operator I spoke with. There are no local Santander bank branches in my state. How can Santander bill for a fee and for what after the account has been closed since - 2013?