It is a very important question and good to know as well. In case you are exchanging your old phone with a new one, and you have already registered with several e-wallet apps; it is mandatory that you delete all your card details from the apps and then exchange the device. Later when you install the new device, you can get the e-wallet app(s) from Google Play Store or Apple Store and re-add your debit cards again to the app. You can follow the aforementioned procedure to add your bank details back to the app.