Product: Vehicle loan or lease

I took out a loan with Santander Consumer USA in XX/XX/XXXX. They gave me this loan which LITERALLY set me up for failure. I got XXXX  a couple months after I purchased the car and was put on XXXX for the duration of my XXXX due to XXXX Then XXXXXXXX XXXX XXXX while I had an infant. I ran into some hard times upon which they repossessed my car without any notice which gratefully my Aunt paid to help me get my car back. Upon getting help with those hardship times they made me sign pages upon pages of paperwork. My Aunt has worked in mortgage loans her whole life, which although a bit different, she understands car loans very well. I have been making payments forever and it doesn't seem like my payments are ever touching the principle. So, I gave my Aunt my transaction history and asked her to go over my loan and help me understand. They gave me a loan for XXXX on a XXXX vehicle with a payment of {$550.00} a month. First of all, I was in a tough place at the time that I got the car, in fact, I was only doing side jobs to make money, I didn't even provide them with proof of income. My Aunt looked at everything I sent her and discovered that my interest rate is fluxuating when the contract I signed was a fixed interest rate. Also, they have my term end for XXXX of XXXX, which if you calculate my remaining debt of {$15.00}, XXXX at {$550.00} a month, EVEN IF the entire payments went to principle, it will NOT be paid off at the maturity date they have on my account. AND WE KNOW that there will be interest. So, my Aunt advised that I call Santander and request copies of all documents on my file which contain my signature - and they refuse to give me anything except the contract which I informed them that I already have my dealer copy. When I asked Santander about the maturity date and debt still owed not adding up- they said they have made modifications to my loan. Which again, they refuse to provide me copies of. I have gathered that I WILL NEVER get this car paid off because when I do my calculations, almost my entire $ 551 monthly is going to interest. I asked Santander if I was supposed to be qualified for the Class Action Suit they had and they told me my vehicle loan was not obtained during the time frame of that suit. I told them that my vehicle was purchased on XX/XX/XXXX and the ending date of the lawsuit time window was XXXX of XXXX. The customer service rep shuttered at my knowledge and still insisted that either way, I did not qualify. I am at a loss because not only has my XXXX XXXX XXXX had 3 major breakdowns leaving me without a vehicle causing me hardships and barely runs at this point, but also I cant seem to get it paid off so that I can get myself and my XXXX XXXX XXXX into a safe and reliable vehicle. Can you help me PLEASE? I am desperate to end this madness with this car and loan because this car has literally almost XXXX XXXX XXXX and me many times due to all of the engine/transmission issues but I also cant get the loan paid off because they have my loan set up to where they charge me however much interest they want, seem to add whatever fees they want and modify the loan without any knowledge to me. I would like copies of whatever they have on file as well.