Basically a prepaid mastercard debit (not credit) card from giffgaff with zero fees and no annual costs. i think it'd be easier for customers to receive payback and it would save some money in commissions to giffgaff when customers top up, need a refund, recurr the goodybags on that card and also the paypal fees when sending out money to customers that want to redeem the payback in cash. this card would be given only to members that have been with giffgaff for more than three months and in case the member switches to another provider, can keep the card for a small yearly fee that will disappear as the member switches be back to giffgaff.

TIM (Telecom Italia Mobile) a carrier in italy, have recently done this starting the service as TIM Pay.