You can freeze your Virtual Card in the mobile app by navigating to More > Cards > swiping left to the Virtual Card > and enabling the 'Freeze card' toggle.
In the web app, navigate to Cards > selecting the Virtual Card > and enabling the 'Freeze card' toggle.
After freezing your Virtual Card, all Virtual Card transactions will be declined until you unfreeze it. To unfreeze the card, disable the toggle.
Please note that your physical Novo debit card will stay active unless you also freeze it.