Answer: Use the UOB Absolute card to top up GrabPay (1.7% rebate), then use GrabPay Mastercard to pay anybody that accepts Mastercard, with GrabRewards points. If you insist on a cardless mobile payment then use GrabPay QR or GrabPay Mastercard with Samsung Pay. With Samsung Pay you get some Samsung points, too. (Or use Standard Chartered’s Spree Visa directly with Apple, Google, or Samsung Pay for a flat 2.0% rebate on the first S$3,000 per billing cycle.)
If you use GrabPay Mastercard to pay your monthly mobile phone bill, you get a bit of AIG mobile phone insurance, too.