Sign in to your Nintendo Account
Go to the Nintendo Switch Online membership page
Select the account with the active membership
Choose Automatic Renewal settings
Turn off Automatic Renewal
Confirm the cancellation
If you subscribed through the Nintendo Switch eShop, cancel there
If you subscribed through the Apple App Store, cancel in Apple Subscriptions
If you subscribed through Google Play, cancel in Google Play subscriptions
Check your email for a cancellation confirmation