You can see all pending transfers in your account inside the "Activity" tab. Within the tab, you can see all your pending transactions at the top of the page. If you want to cancel the transfer you can click into the pending transfer and click the red "Cancel deposit" to cancel the transfer.
There is a limited window to cancel transfers. For wire transfers, there is approximately one hour to cancel from initiation if initiated during a normal business day and business hours. For bank ACH transfers you can request a cancellation prior to 12:00 pm PT on the business day it's made if an ACH Transfer is initiated after 12:00 pm PT on a business day or initiated on a non-business day, you will be able cancel it up to the next business day prior to 12:00 pm PT.