I am currently on a T-mobile postpaid plan. Hypothetically, if I replaced my current smartphone with a micro-SIM card to a smartphone with a different sized SIM card (ex. iPhone 5), I would need to purchase a new SIM card (nano sim in this case). I think the price was $10.
Is is possible to purchase a T-Mobile prepaid SIM card (on sale online occasionally), and activate that nano SIM card to my current plan? Can I use a prepaid SIM on a postpaid plan? What is the price for activating the SIM card when I already have purchased the SIM card?