unlocked iphone replaced with a locked one

ONLY the carrier the phone is locked to can authorize unlocking it. Contact the carrier to whom the phone is locked. No one else can do anything about it.

iPhone was replaced and after that was locked, why?? And now how findout what is that carrier?

That's because the original phone had been hacked or jailbroken to unlock it. The replacement is locked in the same way the original was and would have been had it not been modified.

If you don't know who the carrier is, then call Apple and give them the serial number of the phone. They can tell you. Unfortunately, since you were not the original owner of the original phone, which has now been replaced, it is highly unlikely that you will be able to get it unlocked at all.

As i say i call Apple and they answer that dont know who the carrier ))))

iPhone not jailbroken, cose iOS 8.3

Then you are out of luck. Ask whoever you bought the original phone from before it was replaced, though as I've already said, at this point, you're probably hosed. The replacement will not be in the original carriers database. The best case scenario is you figure out who the carrier is, either from whoever bought the phone originally, or by trying different SIM cards until you find the one that works, and sign up for service with them. After some period of time, you may be eligible to have it unlocked.

i guess you right, but its too strange, becouse all activation path throught Apple Servers )) and now they dont know .... I dont know what happend with Apple, before all my troubles fixing in hours, now they not even call backб as promisse ...

Your problem started when you purchased a hacked/jailbroken phone.

IT NO HACKED NO JAILBROKEN!

100% sure!

The one you have now isn't. The one you originally had was.

If you had purchased it from a legitimate source to begin with, you wouldn't be asking how to find out what carrier it was locked to.

We can't help you. We are users. We don't have access to Apple's database and neither does any third party. Only Apple could look it up. Odds are the phone came from a different country, which it why when you asked Apple, they couldn't tell you what carrier it is locked to.

I ask it becouse my problem is same as Boris. Look at first his message, he bought sim-free, after replace it go lock. After chatting it sim-free again. That is the point! Thats why i ask about carrier becouse i wish findout it and maybe call to support to tell him unlock or help me with my problem.

And i make order to check IMEI of my iPhone and all info about it look very same like Boris.