How to Chalk up $500 for Frank Card
You can go down to a SP service counter(tripleone somerset has one) and pay your monthly electric/water bill using your credit card. You do not need to cancel your GIRO as it will detect your credit card payment and not bill you again if you have already paid for the month.
For your teleco bill, pay via vBox as it will be counted as an online credit card payment which enables the 6% rebate. So assuming $200 for sp service bill, $50 for teleco bill and $50 for mrt, thats already $300.
The other $200 can be easily fulfilled if your charge your groceries and weekend dining on the card within a month. Do note that NTUC accepts nets flash pay, which means, this portion will be counted in the 6% rebate. If you charge your monthly bills to your card and follow a fixed routine, you should be able to hit the $500 mark easily without overspending.