Copy and paste straight from https://www.shopback.my/visa.
See below in bold.

Steps to ensure successful Cashback:
1. Make sure your cart is empty before clicking through ShopBack.
2. Enter the first 6 digits of your Visa credit or debit card to access this page.
3. Click through this campaign page to the merchant site.
4. Pay with Visa card as usual within the same session.

Terms and Conditions:
1. 20% Cashback is valid from 8 Aug, 12.00 AM to 10 Aug, 11.59 PM (both dates inclusive).
2. All 20% Cashback is capped at RM100 per order except for Lazada store. 20% Cashback for orders from Lazada are capped at RM80 per order.
3. 20% Cashback is not applicable to GoShop, Malaysia Airlines, Grab, Love Bonito, Doublewoot, Bonds, HungryGoWhere, Eatigo, PapaDelivery and Happy Fresh.
4. Valid only for checkouts with Visa through the promotion page at https://www.shopback.my/visa. ShopBack reserves the right to deny Cashback to purchases not made with Visa cards.
5. ShopBack reserves the right to modify, amend or discontinue any part(s) of this promotion without prior notice.

SCMOC1595hr4o maxis code 15%
MYMAX10aao3i7 maxis code 10%

Let others know if u have used them.