Downloaded @calm, forgot about it and have been charged $80 subscription fee after my seven day free trial without any notification of this! When I’ve queried it, @AppleSupport say it isn’t eligible for a refund. 
Apple does not allow developers to issue refunds or cancel subscriptions. We've found this article helpful to guide users on requesting a refund: https://www.imore.com/how-to-get-refund-itunes-app-store … good luck! 