In order to pause your card, please go to the "finances" section of the home screen. Here select the appropriate card you want to pause and just click "pause card". 

If you want to block it, a "block" option should appear under the card, after clicking pause.

Please note, however, that after blocking the card, this operation cannot be undone.

You can also remove your card, but this is not recommended for the time being. You can easily order your new card in the application.