Product: Credit card or prepaid card

On XX/XX/XXXX, I identified a late fee issue on my Macy 's American Express Account, issued and administered by Department Stores National Bank. The crux of the issue is that I had scheduled auto-pay on my account for years. Macy 's changed the due date for my payments to the day before my scheduled auto-pay, failed to notify me or update my scheduled auto-pay to match the new due date, and subsequently charged me late fees and minimum interest charges  since XX/XX/XXXX. At no point did Macy 's attempt to contact me to fix this issue, and instead just sat back and collected late fees on my account for years. Also I want to note, there is nowhere on Macy 's credit card website where a user can simply change their automatic payment date. I called customer service and reached out through the chat feature on the credit card website. I was issued a partial refund totaling {$170.00} for late fees incurred on my XX/XX/XXXX, XX/XX/XXXX, XX/XX/XXXX, XX/XX/XXXX, XX/XX/XXXX, and XX/XX/XXXX statements. This refund was applied to an outstanding balance on my card and I received a check in the mail totaling {$150.00} ( which I have not cashed ). I initially requested copies of all my statements since I opened the account ( these are not all posted online nor are they emailed ). I was told I would have to pay {$3.00} per statement, and then I was told I could request them via mail for free. I placed a  letter in the mail on XX/XX/XXXX. I subsequently received and reviewed all my statements on XX/XX/XXXX. I determined this issue went back to XX/XX/XXXX, and calculated my total loss to be {$840.00} XXXX less the amount partially refunded, {$170.00}, meant I was still owed {$670.00} ). I emailed Macy 's demanding to be refunded the remaining {$670.00}. Macy 's responded that they were not monitoring the online message portal due to COVID, and I did not know this because I didn't get an email to my personal email that I had a message waiting in the secure portal. Once I logged into my  account online, I sent another email on XX/XX/XXXX again demanding the remaining {$670.00}. On XX/XX/XXXX, Macy 's  responded that I had already been issued a refund and I was not eligible to receive any additional refund. There was no explanation given in this email. I responded XX/XX/XXXX stating that this was unacceptable to me and asked for the issue to be elevated. Macy 's responded XX/XX/XXXX with essentially the same message - that my partial refund was approved by a manager and I was not eligible for any additional refund, again with no explanation. I have so many issues with everything that has happened with this case, from first being charged these fraudulent fees, to my experience in simply trying to rectify this mistake by Macy 's. I fully believe I am entitled to full compensation for this issue, especially since I've already been issued a partial refund. I never agreed to only a partial refund. The responses I received from Macy's/American Express/Department Stores National Bank are very poor with no detail or explanation. At the end of the day, we are talking a pittance to this credit card company, and I shudder to think about how many other customers have been affected by this extremely unethical and fraudulent business practice.