T mobile $30 prepaid card and iphone?

How do I get the $30 prepaid (unlimited web, talk, and 100 minutes) card to work on an iphone 4s 16gb phone?

I don't have an iphone, but I plan to leave sprint as well as upgrade from my itouch 3rd gen in the process so this seems like the most sensible way to do so. I heard I need an unlocked iphone was needed? I was wondering if there was any way to insure it too?

Thanks for feedback.

Added (1). By switching I mean I'm not gonna be with sprint at all and start fresh with the plan I stated with the unlocked phone that I'd have to purchase separately

Your phone has to be unlocked because T-Mobile doesn't carry the iPhone. Unlocked phones are more expensive to buy than locked ones on contract.

You can't switch a Sprint iPhone to T-Mobile. They use different kinds of networks that are incompatible (CDMA vs GSM).

As it is said that and we know that unlocked phones are more expensive to buy than locked ones on contract. Any ways you can get the $30 prepaid card from the site a given you and also you will get the all international prepaid cards to use.