Yes. When you begin your subscription, you're able to receive a 50% refund of subscription fees if you cancel your subscription within the first 6 hours of becoming subscribed. Beyond the first 6 hours, there are no refund policies and you are required to pay 100% of your subscription fee.
In case you're not happy with your car and not eligible for a refund: In most cases, car owners will give you an option to swap vehicles at a $49 fee during your subscription. Please check with your car provider about the details.