If your voucher is already applied but you want to change it to another voucher, here’s what you can do:
Click the ‘Change’ button on the applied voucher section on your transaction page
Choose ‘Use’ on another voucher that you want to use on the ‘Available Vouchers’ page.
Don’t forget to read the terms and conditions of the voucher first by clicking the ‘View details’ button.
Click the ‘Back’ button on your phone to go back to your transaction page.