Product: Vehicle loan or lease

My car loan is through Santander Consumer USA and was legitimately repossessed in XXXX of XXXX due to me having fallen 3 months behind on my payments. When I called ( after the repossession ) to verify the necessary reinstallment amount to reclaim my vehicle and bring my account current, I was informed that the amount necessary to reinstate was {$1200.00}, but when I requested email or mail documentation from Santander to review the explanation of specific fees and charges that brought my balance to XXXX, I was informed by the customer service agent that Santander would not and had no obligation to provide such documentation in the case of repossession. I did not question the denial of my request any further, but do take issue with this business practice and would like to find out if, in fact, a lending institution is lawfully allowed to refuse such a request. 
On XX/XX/XXXX I made payment by phone of {$1200.00} ( which included my XX/XX/XXXX monthly payment of {$240.00} ) to reinstate my loan and bring my account completely current and to a {$0.00} balance. 
When I went to view my account on XX/XX/XXXX, I was shocked to view that even though I hadn't yet made my XX/XX/XXXX payment, my stated balance was {$940.00}. When I clicked on " statement history '' on my account page, there was absolutely no explanation of what the additional {$700.00} was that I was being billed for. I called Santander immediately to resolve the issue and connected to a customer service representative who could not in any way give me a satisfactory reason for the {$700.00} charge. Her only explanation when I presented the fact that the {$1200.00} consisted of the three missed car payments totalling {$730.00} and the additional 3 months of late fees of {$12.00}, totalling {$770.00}, which left a remainder of {$430.00} charged to me for repossession fees, storage, transportation and auction fees, all having been paid on XXXX XXXX, and brought my account current, she put me on hold for almost 15 minutes with no explanation. I then demanded to speak to her supervisor and put on hold for another 9 minutes until a customer service supervisor, named XXXX came on the line, and I had to detail the issue all over again. XXXX and I reviewed the account with what minimal information was available to him, and he agreed that the balance due was inaccurate and there were duplicate charges assessed to me. He could also not inform me as to the specific breakdown of the charges and fees showing currently or the charges and fees that the {$1200.00} comprised of. As a result, he told me the only recourse was for him to submit a request ( confirmation # XXXX ) for further details and account balance correction to another department and I would be contacted no later than by Thursday, XX/XX/XXXX with a resolution to the issue. 
I emailed and called Santander several times after no one contacted me by the promised date, with no response whatsoever and was told no information was available to the customer service representatives I spoke to as well. 
When I called back this morning ( XX/XX/XXXX ), I was connected to an extremely hostile agent who could not intelligibly communicate or tell me what the result of the account review that XXXX had requested 10 days previous was. She persistently interrupted and talked over me, so that after 38 minutes on the phone with her, in frustration, I decided to disconnect and call back in chances that I would speak with a better informed and gracious representative. When I called back, I was put in touch with an agent named XXXX. Once again, I had to detail the billing issue and my dispute. After reviewing my account at length, XXXX concurred that the account balance was erroneous by his calculations and information accessible to him. He assured me that he would forward an additional request for account correction ( confirmation # XXXX ), and the issue will be resolved in 48 hours, which based on previous personal experience, is unlikely. 
If left unquestioned, a total of {$1100.00} will have been added to my account for miscellaneous items by Santander Consumer USA. 
Please assist me in preventing consumer XXXX and unprinciped practices employed by this company. 

Thank you, XXXX XXXX