I'm happy to help you with this :)
Since all purchases through our App are managed by iTunes they're the ones who handle any cancellations and refunds! You'll have to go into your iTunes subscriptions to change your settings for the app. Here's an article explaining how to manage/cancel your subscription for it:
This is the basic idea:
Go to Settings > iTunes & App Store.
Tap your Apple ID at the top of the screen.
Tap View Apple ID. You might need to sign in or use Touch ID.
Under Subscriptions, Tap Manage.
From there they can manage/cancel their subscription.
If you're looking for a refund or have any other issues with a purchase through iTunes here's the link for you:
Please let me know if you need any help! 😊
Chany & the Optimize Team