Transfer phone number to different device and SIM

I currently have a Samsung Galaxy S2 with $30 /month 100 minutes prepaid plan (using regular size SIM)

I plan to buy the T Mobile Iphone 5s full price ($650) from Apple store (without activation at the store).

Is it possible to have my current phone number in Galaxy S2 (with $30 prepaid plan) transfer to the Iphone 5s using nano SIM ?

I need to know before buying the Iphone 5s.

Thanks
Steven D.