Yes, you can! However this is only for Android users.
If you are not connected to data/wifi, simply go to the app:
1. Click on "ME"
2. Click on "View my saved vouchers" and you will be prompted to your saved vouchers.
3. Click on the voucher you want to redeem and you will be prompted to your voucher page. Click on "Send an SMS to redeem".
4. You will receive a SMS with the 4 digit redeem code.
5. Enter it on the page to redeem.
6. Your voucher is now redeemed successfully!