Product: Credit card

Dear Sir : My Credit Card company ( Continental Finance Company, " XXXX '' ) imposed a late fee on XXXX XXXX, 2016 of {$35.00}, which I dispute. The reason I am disputing this late charge is that the Credit Card company failed to properly process on on-line payment of {$510.00} from my bank account, and thereafter failed to notify me of any such payment problem until after the late charge was imposed. 
This payment was made through the Credit Card company 's on-line payment system on XXXX XXXX, and I received an e-mail verification confirming the payment. This payment should have brought the credit card balance to {$0.00}. 
On XXXX XXXX, 2016 ( 26 days later ) I attempted to use the card, unsuccessfully. When I called the Credit Card company to investigate, I learned that the Credit Card company reversed the on-line payment as a " returned check '' on XXXX XXXX. However, in contacting my Bank ( XXXX XXXX ), they were unable to locate any " returned check '' or declined payment transaction out of this account, and at all times I had more than ample funds to cover the {$510.00} payment. 
I then contacted the Credit Card company further on XXXX XXXX, 2016 and spent perhaps 90 minutes on the phone on this matter. First, I once again furnished my bank account information and they immediately processed a payment for {$510.00}, so that there would be no outstanding payment issue. Second, I requested that the {$35.00} late fee be reversed, in view of the evidence that I in fact had made a payment to them on XXXX XXXX. The Credit Card company has refused to reverse this charge, which I am now disputing. I then asked for evidence of the " returned check '' event on XXXX XXXX so that I could ascertain what the problem was. The Credit Card company refused to provide this information, " for security purposes. '' The conversations on XXXX XXXX were with " XXXX '' ( a customer service agent, who was polite and pleasant ) and with XXXX XXXX ( a supervisor, who was somewhat more difficult -- derisive and belittling ). 
On XXXX XXXX, 2016 I followed up again with the Credit Card company, this time speaking with a supervisor by the name of XXXX XXXX. XXXX XXXX similarly refused to reverse the late charge, making the statement that it " had to have been my fault '' that the payment was not processed correctly, but similarly refused to provide any evidence of the XXXX XXXX " returned check '' transaction on which they are basing the late charge. Somewhat bizarrely, XXXX XXXX then stated that because this was on on-line payment through their website " we have nothing to do with that. '' When I inquired how I could have corrected this payment issue, XXXX XXXX did state that a Notice that my account had been " revoked '' was sent to me on XXXX XXXX, although no such Notice was ever received and XXXX XXXX similarly declined to furnish a copy of that Notice as well. 
From my perspective, a payment of {$510.00} was properly made through the Credit Card company 's on line system, and verification of the payment was received. The Credit Card company now states that the payment from my bank was somehow declined on XXXX XXXX, but refused to provide any evidence of that. No notice was ever received of any payment problem, until I learned on my own of an issue on XXXX XXXX. The late charge was imposed on XXXX XXXX. 
I thank you in advance for your assistance.