Everyone here must know this info:
Turkey is very stupid country . Every person when enter Turkey border must leave his mobile because it is locked from operator !!!!
You must pay thousands Dollars to get registered IMEI !!! (New Phone).
?
Nobody has to leave their phones on the border. But if it's locked, obviously you won't be able to use it with any of the Turkish GSM operators. That's true for any country, not just Turkey.
And to register a new phone purchased outside of Turkey you have to pay around 50$ to get it registered, not thousands of dollars.