A:AnswerI don't know the answer to that question. The Best Buy associate did all the set-up and activation of my phone when I purchased it. Why don't you just ask at Best Buy.
A:AnswerYes, using an AT&T sim card will not lock the phone to the carrier. The phone has been sold unlocked and will remain that way. The carriers do send settings to the phone to allow the phone to access their data network, and those will change again when you use the new carrier's sim card after the AT&T Now one.
A:AnswerThere was no catch. The Samsung 10e was as advertised. Picked it up at my local Best Buy and the Geeks in the cell phone department set it up for me and transferred my files. I didn't change carriers so can't comment on the advantages of the phone being unlocked. Be aware that this phone is physically the same as my old 5s, but the screen takes up the front of the phone.