SIM to new phone & keep #

Hola,

I'm pre-paid and I need to upgrade my old phone as 3G is ending next month.

I have my own new unlocked iphone.

I bought a SIM card from my online T-mobile account from the "upgrade my device" menu.

Please A B C see it for me to activate the SIM card online & keep my number.

¡Gracias de antemano!