If you need to cancel a card order, you have two options.
If you have Account Owner or Admin rights, go to your Cards tab, select the card you've just ordered, click on "Mark as lost / unused / damaged / stolen". Then, click on Order a new card if you need to order another one.
If you don't have Account Owner or Admin rights, ask them to do it for you. It's indeed not possible for a Requester to cancel their card if it's not activated.
If you're unsure of who your Account Owner or Admin is, reach out to your favorite support team at firstname.lastname@example.org 😉 .