How to change (upgrade, downgrade or cancel) the subscription details are available on Integromat Support website link https://support.integromat.com/hc/en-us/articles/360008439134-How-to-change-upgrade-downgrade-or-cancel-the-subscription

Always refer to above link for latest process and policy applied as per Integromat from the above link.

You can manage your subscriptions under the “Subscription” tab as shown below: