Verified answer

It sounds like a factory unlocked phone but you should ask the seller to make sure.

Never Locked Iphone

2

in case of iphone 5s if its part no. is below 300 then it is 100% factory unlock or sim free phones and second thing is if on the back side of the box is mentioned that this phone support gsm and cdma then it is chances of lock phone so purchaes only gsm support phones

It should mean that this Iphone can only been use with the SIM card from the service provider where you get your Iphone and no others.

Just go YOUTUBE and type "unlock iphone", think you might get more info from there.

"never locked" = "you can upgrade the firmware anytime and it will never lock back up"