Help - how to resolve disputed

car rental charge. I got a bill for almost $2000 for a one-week rental. I tried to resolve it with the car rental company. They would only refund me $200.
Then I tried to dispute the charge through my credit card company. They said they cannot intervene since the contract does not clearly support my argument. However, the contract is so poorly constructed and it does NOT support the car company's argument as well. So why do I have to take whatever they want to charge me. My credit card company now ask me to pay the bill immediately. What should I do? If I take legal action, I'm sure I have a good case of false/misleading contracts. But I do not know how to start. Please give me some advise. Thank you.