Please use this link: Cancel subscription to cancel your paid subscription or trial.
Your account will then be downgraded to the free MindMeister Basic Edition at the end of your license period and you won't be charged anymore.
You are able to fully close your account here: Close Account once your license period or trial expired. If you would like to delete your paid account completely please contact support for assistance.
Cancel your subscription (iOS)
Subscriptions you've created via the iOS app are managed by iTunes only, which is why we unfortunately cannot handle those cancellations or refunds ourselves.
Please see this article for more information on how to manage your iOS subscriptions: View, Change or Cancel Your Subscriptions