You can lock your card at any time to stop new charges, no need to explain why. Unlocking it restores full use. This is useful if you've misplaced your card and want to pause it while you look, or just want to temporarily prevent any spending.
How to lock your card
Select Cards
Select the three vertical dots on the card you want to lock
Select a reason and Lock Card
How to unlock your card
Select Cards
Select the locked card
Choose Unlock Card