I've deleted the Android Pay app but can still make payments. Why?
Android Pay stores your Virtual Account Number on the phone. It is the Virtual Account Number which is used to process transactions rather than the Android Pay app.
The Android Pay app is used to manage your cards and provide the Android Pay Transaction Receipt. It is a term of the Westpac Android Pay Terms and Conditions that you keep the Android Pay app installed on your phone so that you can receive the Android Pay Transaction Receipt.