Tap the hamburger icon on the top right of the home screen.

Tap "Payment Methods".

Tap on the bank account you want to unlink. A pop up will appear from the bottom of the screen. Tap "Unlink".

On the 'Confirm unlinking' pop up screen, tap "Unlink" to proceed with verification.
​Verification screen will appear to verify this action via biometrics or by entering your passcode.

You will be taken back to the payment methods screen with your bank account removed after successful verificaiton.
​Your account is now unlinked from your Bookipay app.