Freezing a card means you’re temporarily blocking it from being used, whereas cancelling is permanent and cannot be undone. You can freeze or unfreeze any primary or linked card as often as you need.
Note, freezing a primary card will not affect any of its linked cards.

From the cards page, select the card you’d like to freeze. Then click the more options menu (3 dots on the lower right side) and select “Freeze card”. This will take effect immediately.

You can repeat the process to unfreeze the card.

When a card is frozen, all point-of-sale transactions, ATM withdrawals, and automatic payments will be blocked. These will be enabled again when you unfreeze the card.