HKtraveller, I think that what transpac is saying is that you can change the expiry date/plan/promotion at any time on any prepaid 1 2 Call sim. It is a matter of "software" (the plan/promotion) function vs. "hardware" (the sim) function. The expiry date is not "hardwired" into the sim. Both of your plans/promotions and in effect expiry dates terms can be changed in either of your sim cards. Your sim cards may look different on the outside but they function the same.