Hello! Do check the terms and conditions of your existing car insurance policy to find out what happens if you cancel it. Generally, if you cancel it before it is time to renew, the insurer will pocket about 30% of the unused portion of your insurance, leaving only about 70% as a refund for you.
If you can, wait until your car insurance is up for renewal. Then you'll have the freedom to switch to any insurer you like without any penalty.
By the way, you may not always be the one walking away from a car insurance policy. There are also situations where your insurer might decide to drop you (sometimes with no refund at all) if they think there's foul play or illegal modifications going on.