Cancel a NV Charts App chart subscription.
In order not to automatically renew the subscription in the next year, you must cancel the subscription in the operating system settings. (Of course, you can reactivate the subscription at any time when you get back on the water. Possibly also in another region)
For iOS this is described in detail here: https://support.apple.com/en-us/HT202039
Go to Settings > [your name] > iTunes & App Store.
Tap your Apple ID at the top of the screen, then tap View Apple ID. You might need to sign in with your Apple ID.
Scroll to Subscriptions, then tap it.
For Android this is described in more detail here: https://support.google.com/googleplay/answer/7018481?co=GENIE.Platform%3DAndroid&hl=en
On your Android phone or tablet, open the Google Play Store Google Play.
Check if you’re signed in to the correct Google Account.
Tap Menu Menu and then Subscriptions.
Select the subscription you want to cancel.
Tap Cancel subscription