How do I stop the automatic renewal of my Premium or Premium+ membership?

This will work only if you subscribe to the web version of the game. If you play via the Google Play Store or the Apple App Store, you can manage your subscription directly in your profile on these platforms.

You can cancel the tacit renewal of your subscription at any time, even just after you have subscribed. To do so, go to your profile.

On the page, you'll see a "Manage my subscription button". Then, on the next page, you'll see a "Cancel my subscription" button. Hit it and it's done!

This will not prevent you from reactivating the renewal later if you wish!