In order to block or cancel your card follow these steps:
1. Log in to your Profile
2. Go from your dashboard to the "Cards" section
3. Click on the card you wish to block
4. A pop-up menu will appear where you need to click on "Report lost or stolen"
5. Then you will be asked for the reason you wish to report, and if you just wish to block it.
After finishing these steps you may order a new card by following this guide