IPhone says T Mobile instead of Simple Mobile?

So I got a new iphone today and i had to cut the sim card down for the 4s. So when i finished and put it back in the phone, it says i have T Mobile, but it is a simple mobile sim card? When i used the simple mobile sim card for the 3GS it said "simple mobile" but now that i changed it, it says t mobile. Does anyone know why this happened? And am i being like charged? Is it because i cut the card? I'm really worried right now >_<"

Simple Mobile uses T-Mobile's towers. Your iPhone can't discern it because it's basically the same service.