Product: Vehicle loan or lease

As of late XXXX of XXXX, I have been contacted repeatedly regarding my account being late by GM Financial. I was advised that the amount paid on XX/XX/XXXX was credited toward some alleged balance on our prior lease. This payment was made ( actually overpaid ) for XX/XX/XXXX on my current lease. I was advised that I still owed the amount for my current lease and all applicable fees. 
I was advised by the GM financial rep that the payment made on XX/XX/XXXX was applied to " excess wear and tear '', which I had not been previously informed of nor had I signed off on any acknowledgement of said alleged damage. The GM financial rep advised me to contact my local dealership where the transaction was performed, which I did. 
On XX/XX/XXXX, a representative from my local XXXX dealership advised me that he had spoken with GM Financial and found that not only was there not an account balance on my previous lease, but that I had overpaid on this lease. This was acknowledged by your company when you issued me a refund for overpayment on previous lease on XX/XX/XXXX. I made several follow up calls to GM Financial, beginning on XX/XX/XXXX, regarding whether or not the refund that I received on my previous lease was part of the payment that was made in XX/XX/XXXX. 
I was initially advised on XX/XX/XXXX when I spoke with an operator named XXXX and and XX/XX/XXXX when I spoke with a female operator named XXXX that the refund that I had received in XXXX of XXXX had nothing to do with the current lease and that the payment would be applied correctly to my account " as soon as a manager approved it ''. I continued to check my online statement and found that not only was the " missing '' payment not applied, but that they continued to assess late fees to my account. I continued contacting GM Financial to attempt to rectify this issue. 
I made calls to GM Financial on XXXX, speaking with XXXX and also on XXXX in conjunction with making my payments during those months to inquire as to the status of this situation. I was told in the XXXX phone call that I would be responsible for the full balance, which I disagreed with. During the XXXX phone call, I was informed that I would be able to pay the " missing '' payment, but that all of the late fees and charges would be eliminated. 
I gave this some time to process and I did not see any change in my balance. I then contacted GM Financial after discovering that they placed a 30 day late payment on my credit report. I called and spoke with a GM financial rep named XXXX on XXXX. XXXX  initially advised me that she didn't think that the refund had anything to do with the late payment or the refund, but then advised that it did appear as though the misplaced payment was contained in the refund that sent in XX/XX/XXXX, which was contrary to the first 2 representatives that I spoke with in XXXX. I asked XXXX about the late fees and charges and she stated that I was liable for the charges, to which I advised her that I would not be paying them based on this odyssey that we'd been involved in. XXXX   advised me that she would consult with a manager and call me back on XXXX. As of XXXX XXXX  on XXXX, I have not received any contact from GM Financial.