A guy is trying to sell me his "carrier unlocked" iPhone 4s Sprint for $400. I think its a pretty good deal, but the only issue is that I have T-mobile. I was wondering if there is such thing as a carrier unlocked Sprint iPhone 4s? If so, will it work with T-mobile? Sorry if this has already been asked, but I've been searching the web for hours trying to see if this would work. The only think I've found is that Sprint unlocks the iPhone 4s for international carriers ONLY, and not domestic carriers... is this true? Thanks guys!