You can change the Card Wallet you want to use through the "Scan new card" menu.
Click the "Scan new card" menu and tag the another Card Wallet.
Change Card PIN
You can change the current PIN of your Card Wallet. Please proceed in the following order.
1) Enter your current card PIN number
2) Enter a new PIN number
3) Enter the new PIN number once more
4) Tag the Card Wallet on your mobile phone