My understanding is the sim free iPhone 6 6plus is the same model as Sprint's in which all current bands for cdma gsm are in there to make it a "world phone." Getting the sprint device domestically unlocked after its been paid off on an account in good standing etc seems to be available but anything but flawless as it takes a few days and many results have been just an international unlock before having to call cs again and have them "multi" unlock vs international. My wife saved up bought an iPhone 6 sim free which the store reps at sprint back home were baffled as they set it as they did not seem to be in the loop but the imei or whatever was in fact white listed in its database and she left a happy camper being on the 50 unlimited everything plan (we don't travel much sprint works in my area lte anywhere from 3-15mb not yet a spark site).
I am not disciplined so am financing my iPhone 6 plus through them and they credited my account from changing from my prepay carrier $100 as it was the end of the month and they put us on a 2 line 100 month unlimited plan so my small credit union discount could be applied.
I owe an additional 38 a month or so on the phone over 24 months but when/if I decide to pay it off early I plan on having it unlocked for the sake of ultimate freedom/choice to bring my device anywhere in case a better deal comes or sprint folds lol.
