you can cancel by opening the cash app and tapping the clock icon in the top right corner. You need to select the account to which you sent the payment and choose "Cancel payment" at the bottom of the screen. If you do not see an option to cancel the payment, it means that it has been completed and can no longer be canceled. If you want any more information about it visit the https://www.cashapphelps.com/blog/cash-app-refund-number/