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I'm Lucy, and I'd be happy to answer your questions today.
The 3-day right to cancel is a concept that unfortunately only applies in very limited circumstances, such as door-to-door sales. It does not allow a person to cancel all contracts within 3 days, and it doesn't apply to automobile sale or leases. Read your lease carefully - if there is any right to change the terms or walk away, it would be in your specific contract.
It is sometimes possible for a dealership to help you renegotiate a sale if you're not happy with your purchase. They do this as a show of good faith, because they get business from referrals and repeat customers - especially with leases. If you're happy with your lease, then you might come back. So it could be worth talking to the sales manager, the person who sold you the car, or the overall general manager to see if anyone will help you out. But there's no general right to cancel.
I apologize that this was probably not the Answer you were hoping to receive. However, it would be unfair to you and unprofessional of me were I to provide you with anything less than truthful and honest information. I hope you understand.Good luck.