First of all, you need to block it immediately. Please go to your “Wallets”, choose the card’s wallet and point the mouse cursor on your lost/stolen card. Then press “Freeze card” to block it temporarily, or press “Manage card” to close your card permanently with the “Close card” button. Please, enter your 2FA Code in a popup window to confirm.
You can unfreeze the card at any time, just tap “Unfreeze card” and enter your 2FA Code.