Go to the Billing page in your account and cancel your subscription in a couple of clicks. Your plan stays active until the end of the period you’ve already paid for, and after that your account switches to the Free plan. Or you can choose another plan here.
What happens to my data after I cancel?
Nothing is deleted. Your projects, saved sites and other data are kept in your account, but on the Free plan they’re hidden. Once you subscribe again, everything will be available exactly as you left it.