You can cancel at any time from your account. There is no cancellation fee, no notice period and no retention step you have to argue through.
Cancelling stops the next renewal. It does not end your current period — you keep the plan you paid for until that period runs out, and the account then drops to the free plan rather than being closed.
Your history and settings stay in place after a cancellation. Cancelling is not the same as deleting your account, and if you want the data gone as well, that is a separate request.
Because card payments are not live yet, there is currently nothing to cancel. This article describes how it will work, and the refund policy is already published so the terms are visible before anyone pays anything.
If a renewal charges you after you cancelled, that is a fault rather than a policy question. Tell us and we will refund it.
Downgrading rather than cancelling is also possible, and takes effect immediately rather than at the period end.
Cancelling does not delete anything you have processed. Your history stays available on the free plan, subject to that plan's limits.
If you cancel and later come back, you start a new subscription rather than resuming the old one. There is no penalty for having left, and no loyalty pricing that a returning customer loses — everyone pays the published price.
Team plan seats work the same way. Removing a seat takes effect at the next renewal rather than immediately, so the person keeps access for the period already paid for.