If you purchase Spiro through the iTunes store you must also cancel through the iTunes store.
Here is an article from Apple that explains how to cancel iTunes subscriptions:
Cancel from your iPhone or iPad:
To view your subscriptions:
- Go to Settings > [your name] > iTunes & App Store.
- Choose your Apple ID at the top of the screen.
- Choose View Apple ID. You might need to sign in or use Touch ID.
- Choose Subscriptions.
- Choose Spiro from your list of subscriptions
- You can choose "Cancel Subscription" to cancel your subscription. Your subscription will stop at the end of the current billing cycle.
If you have questions please contact firstname.lastname@example.org