You can cancel a transaction at any point during the processing time, as long as the merchant hasn’t confirmed it yet.
To cancel from the app, follow these steps:
Go to the account at the bottom right tab.
Select purchase history.
Choose the transaction you wish to cancel, and press cancel.
Good to know:
If you change your mind after the transaction has been processed by the merchant, you will need to go through the refund process, your payments will be fully refunded once approved by the merchant.