You can temporarily block your Suits Me card from your mobile app.
Go to the menu, click on "Cards" and select "Freeze Card". This can be unfrozen whenever you're ready to use it again.
You can do this whenever you stop using your card for an extended period of time, if you can't find your card or if you think it's been stolen.
If you plan on leaving your account dormant for longer you can temporarily shut your account.