You can update, add or remove the card on your account under Profile.
App: Click 'Profile' --> Payment details (third option) -->
ADDING a new card: Click '+' (top right) --> enter info --> Click 'Save'
REMOVE a card: Slide left on the card you want to remove --> Click 'delete'
CHANGE card (if you have more than one on file): Click on the card you want to set as default - this is the card that will be charged
Jiffy Website: Click your name (top right) --> Profile --> Under Credit Cards --> Add, remove or change card here