Click on the center number by the user in user management to see their Payments tab. Click on the 4 dots to the right of the payment you'd like to cancel --> click "Cancel Payment," then confirm the action by clicking "Yes, cancel the payment." 
An authorized payment is a payment that has been made by the user but has not yet been processed by the payment processor. The payment remains in an authorized state for 24hrs, during which time they can be canceled or captured. If you cancel an authorized payment, the user will not be charged and no processing fees will be assessed.
Other types of transactions