I have an iPhone 4s that is configured to Sprint. I think that the 4s models were able to be used on any of the different carriers as there is a sim card tray on it. My question is, can I use this phone on T-Mobile? Specifically I am trying to tell if this phone is the same as the one that T-Mobile sells in their stores right now. If it isn't, would I get the same performance out of it or would I be better off selling it and getting an actual T-Mobile branded one?