To modify your Malwarebytes for iOS Premium subscription or request help with other billing-related issues, access your Apple account to manage your subscription. Apple manages billing inquiries for apps purchased through the App Store.
Managing your subscription
You can access your Apple account from Malwarebytes for iOS > Settings > Manage subscription.
To cancel or refund your subscription, contact Apple support or refer to Apple's article View, change, or cancel your subscriptions. Apple recommends canceling your Premium Trial at least 24 hours before the 30-day period ends to avoid subscription fees.
For other inquiries related to your purchase, such as viewing a receipt or reporting a problem, see Get help with an item purchased from the App Store.