Unlocked iphone replaced with a locked one

Question

Last year in October I bought an unlocked iphone 5s in Thailand, I live in Croatia and  had some issues with the screen and yesterday apple gave me a new replacement iphone, and the replacement iphone is locked. Been talking with Apple support yesterday for over an hour, and they suspect its locked to US AT&T (but not 100 % sure if its AT&T), they can see the store info where I bought it in Thailand but they say they can't do anything to unlock it, so they gave me phone number of AT&T and said they would unlock it wihout problem.
Anyway then I started talking to AT&T support then and been talking to a couple of managers  for over 2 hours, they just keep passing me to another higher level person and in the end they said they couldn't  do anything, their best suggestion was that I go from Croatia to the store in Thailand where I bought to iphone so they unlock it.
I did a online check of my Iphone over IME numberI and this is the info I got:
Model: SVC,IPHONE 5S,GSM,16GB,GRAY,CI/AR
MAC: 78FD94CB1455
ICCID:
iOS Version: 8.0.2
Unbricked: false
Unlocked: false
Activation Status: No
First Unbricked Date:
Last Unbricked Date:
Initial Activation Policy: 52 - US GSM Service Policy
Applied Activation Policy: -
Next Tether Policy (Carrier): 52 - US GSM Service Policy
Status: Locked
Please help,  what should I do?

Answer 1

Whatever you do, do not use the factory unlocks, because then you will never be able to use your phone - this amounts to hacking your phone, which will void any warranty cover and perhaps brick your phone for good.
Anyway, what you need to do is go back to the Apple reseller who gave you the replacement phone in the first place and tell them that you had an unlocked phone and that the replacement they gave you is locked to AT&T and you need to demand that you give you another replacement phone that is unlocked.
If you went to the Apple re-seller for help in the  first place and they were the ones who gave you the replacement phone, then it is their responsibility to give you another unlocked phone and not one that is locked to a network.  They need to replace like with like, so if you went through them, then it is their responsibility and not Apple or AT&T.  There is nothing AT&T can do for you to unlock the phone, as you never had a contract with them in the first place and Apple do not unlock phones anyway - only the carriers, so your first port of call must be the re-seller.
However, if you purchased the phone in Thailand you have no warranty cover for Croatia - iPhone warranty is not international, so to get a proper exchange and warranty cover, you will really need to go back to the Apple store in Thailand where you purchased the phone to get a proper unlocked replacement and this iw what you should have done in the first place.
iPhone warranty is not international so the Apple re-seller in Croatia need not have helped you in the first place, which is probably why you got a locked phone as a replacement, but your first port of call is them, as you dealt with them in the first instance.
They gave you a locked phone as a replacement, so ultimately, they need to replace that locked phone with an unlocked phone as you had.