FRAUDULENT LEASE PRACTICES AND FIGHTING A VOLUNTARY REPO

My question stems from a fraudulent lease term. I agreed on a lease term of 3 years with(name of dealership omitted) Nissan of (name of city omitted). It was the second lease I had with Nissan/Infinity. The first one was 3 years and paid off. I ended up having to keep the car for the first year despite the terms being changed without my knowledge. Until then there was never a late payment but at that time I felt like I was being taken advantage of. I ended up giving the vehicle back and now they sent a bill for over $12,000 dollars. I want to know is there anything legally I can do to fight the unfair and unethical use of agreeing on one thing and getting suckered in that bad deal? How do I go about trying to fix this on my credit because that started a snowball effect? I want to fix my credit standing but with the rising mortagage rates/prices, my wife not working full time, and a new child it seems impossible. Please advise me on what steps I need to take to clear this up. Thanks- Jon - Is this your question? Add additional information