Product: Credit card or prepaid card

I have a Capitol 1 card. My first payment was due on XX/XX/XXXX. Last four digits on that card are XXXX. 
On XX/XX/XXXX, the day before bill due, I made a payment using the Cap1 app in the amount of {$390.00} and I got a confirmation number. Before the confirmation number, the app displayed an error message for a second or two before giving me the confirmation number. 

On about XX/XX/XXXX I called customer service at Cap1 because the money was just sitting in my checking account. The app kept displaying a payment processing / pending message. I had a confirmation number. The operator told me my account was ok, no problem. I asked maybe twice to make sure and I was told everything was fine. 

On XX/XX/XXXX I wake up at XXXX to an e-mailed statement from Cap 1. It had a LATE FEE, interest fee and further said I was OVER MY CREDIT LIMIT ( all tied to the fact that the payment I made did not process ).

I immediately called Cap 1 customer service and paid off the entire balance of {$530.00} ( which includes late fee and interest charge I wouldnt have been liable for had the first payment processed correctly ) I was given a confirmation number again. I was very concerned about the OVER LIMIT info being reported to the bureaus. I was trying to find out what went wrong and I was, in sum, told to contact my bank. I drove to my bank to inquire and XXXX XXXX doesnt show ANY ach attempt from Cap 1.

I have talked to Cap1 3-5 times since then. I have attempted to talk to a manager about what went wrong but I keep hitting a wall. I was told XXXX XXXX ( my bank ) sent a letter to cap 1 BEFORE the statement close date and NO one from cap 1 attempted to make me aware of an issue. I requested a copy of that letter but have been told thats its for internal use only. I wanted to take the letter to my bank to get to the bottom of the issue. The purported letter said the account was closed, and I was told the last 4 digits of that account are XXXX. That account indeed is closed but thats NOT the account I used or input into the payment screen. I dont even have that account number on my files anymore. Something beyond my control went wrong. I asked that same manager over the phone if I can access any info I used to make the {$390.00} payment on XX/XX/XXXX via the app, just to verify. I was told that wont be possible for me to do. 

I called again this morning ( after getting an alert from XXXX  of an 18 XXXX  point drop as a result of this ) to ask if an IT ticket may be opened to find out what went wrong and the rep said NO. I want them to trace the error from XX/XX/XXXX to make sure it doesnt happen again. The manager on duty today told me via phone I know for a fact theres no glitch or problem.

I dont understand how that individual couldve made such a statement given shes not in IT. 

I reiterate, the over the limit info was released to the bureaus and my XXXX fico 8 formula dropped 18 points as a result and I have the screenshots that show it. I made a timely payment which for some reason didnt post and I want a clear investigation as to how the checking account number I input was converted to an old closed account.

I dont feel any goodwill or transparency from Cap 1 toward me. I keep attempting to ask them to trace the original payment via tech support/ IT to see why my info reverted to an older closed account and they keep telling me to take a hike whilst ruining my credit score. 

I know for a fact I did not use the closed account to pay. This is not something Im at fault for. 

Today I was told by them that if Im not happy I can file a dispute with the credit bureaus which would only lead to vicious cycle because, given that the payment isnt going thru, the dispute will only come back as verified because they will verify their statement as correct without fixing the root cause of this issue which is technical /IT in nature. This doesnt even skim the surface of what the true issue is. Its patently unacceptable for them to give consumers this sort of cookie cutter advice because that doesnt not even begin to solve the issue at hand.