In order to cancel the pending withdrawal you need to do the following:
Web version: on the main page of the platform click on "Pending withdrawals", select the withdrawal you want to cancel and click on "Cancel withdrawal".
Also, you can click on "Deposit" and pop-up will appear, suggesting to cancel the existing pending withdrawal.
App: go to Account -> Payments -> there you can see "Pending withdrawals", click on the one you wish to cancel -> "Cancel withdrawal".