Looking to move over to Tmobile with 5 out of contract Sprint iPhone 4s. Tmobile retail said it could be done once phone is unlocked. Called up Sprint and they gave me 5 six digit codes, one per line and said to simply give those codes to the new carrier "and they will know what to do". Can it be so simple? I thought they have to unlock it on their end and somehow iTunes has to be brought into the mix.