Cancelling on iOS
How to cancel/manage an iOS subscription
If you subscribe to GradeProof Pro on the iOS app your subscription will be handled through Apple and we aren't able to cancel them on your behalf. The best way for you to manage your subscription is to go to your iTunes subscriptions settings and turn off "Auto-Renewing" for GradeProof. This will prevent any future payments. If you have any issues with an iOS subscription, you will need to contact Apple directly as we have no access to their payment system.
Instructions for this can be found here: https://support.apple.com/en-au/HT202039