Product: Credit card

I just recently closed my CARECREDIT / SYNCHRONY BANK credit card due to fraud activity that affected/abused me financially by the company. I opened my credit card a few years ago to take care my dental bills, each transaction offered me 0 % interest charge for about 18 month. I spoke with the customer service multiple times to ask them about when my 0 % promotional rate will end. I asked them to calculate and gave me the exact amount for monthly payment and requested for that amount to be taken from my account every month to avoid ANY interest charges, as I was firm that I wanted to pay off my balance before promotional rate would end. 
I stress that I made multiple calls and spoke with multiple agents in the call center just to confirm by asking the same question of what amount to be paying each month. None of them explaining that my promotional rate had ended ... instead they insisted that my 0 % promotional rate will be expire in XXXX XXXX. From my last conversation, the agent told me that I can make a {$400.00} payment every month to pay off my balance and to avoid interest charges after my 0 % promotional rate end. I agreed to do so, I trusted them and set up the monthly payment to {$400.00}. Since I am registered to online statement instead of a paper statement I was just going off of the advice of those in the call center, for they are the foremost experts on the facts and figures around my account, right? After multiple calls and requests, I finally realized that my debt is not going down.. I feel like i have been paying it forever but still have over {$2000.00} in balance. I therefore recently decided to log in, recovered my password and downloaded my previous statement, to see if there was any suspicious activity or fraud. It was then that I noticed a very high interest fee that I 've been paying since XXXX! With it being XXXX that amounted to over {$1600.00} ( from {$3000.00} debt balance ... so over 50 % interest. I just called the call center and escalated to a manager, asking why they charged me the interest fees for months, even years. She took all of the blame off of the employees that misguided me and said I should blame myself for not paying the full amount off in XXXX. I said that I had explicit conversations about this very subject, avoiding fees and when promotional dates ended and she said that those agents were just telling the expiration date of the most recent promotion. This is blatant scheming. 
The reason why I write this complaint because I want to get my interest money back due to : 1. I spoke to multiple agents over different months/years and had explicit conversations about the topic of avoiding interest fees that I now see were incurring on my account. They knew something but took advantage of me. My interest rate will change from 0 % to 26.99 % in XXXX XXXX was all that I was told, and I have time till then to finish my balance. All these credit card agents assured me that I have nothing to worry about the interest charge fee because the promotional will end in XXXX XXXX. 
2. I have asked multiple times about how much money should I pay every month to pay off my debt.. but they lied to me about the amount : They initially did n't set up the amount, and instead told me to keep my monthly payments to {$76.00} for months/years. After I complained about it, they said, i can pay $ XXXX to pay off my balance. I did .... i paid {$400.00} and the truth is they hid the fact that I had interest charges in my account. I was led to believe that paying the minimum amount so they can keep charging me high interest fees per month ... My debt was {$3000.00} .My debt was {$3000.00} and they already had taken {$1600.00} interest fee from my bank account during their shady business since XXXX. 
3. I really want to pursue this matte because I believe the company did fraud and abused me financially. 
4. I request for an investigation