I have a friend in the US and he told me Walmart is selling a couple of models of iPhones 5S for like $149 but they're locked to these US carriers that won't unlock them officially unless you're with them etc.
I remember reading in comments to deals about the iPhone on here that people were inserting a 3 sim as the first sim to basically get an unlocked iPhone.
My question is this: do iPhones really become locked the moment a sim is first inserted? Would this apply to a US iPhone too? Many thanks to anyone who can help and merry Xmas to everyone!