my device was aproved to be unlocked, but it keep locked

Have you checked the locked status on the phone itself?  Look for the carrier lock status line under settings - general - about.

Also, was the approval on Aug 6, or June 8?  Not sure if the 06-08 date format is US style or European style (although it should be US style).  If it is Aug 6, Apple may not have processed the unlock yet (may take a couple of days)

Finally, how do you know the phone isn’t unlocked?  Have you tried a non-AT&T SIM in it? The phone needs to connect, either via cellular or WiFI, to the Apple servers to process the unlock.

it was on june, and it keeps locked :/

:

To complete the unlock, your phone must communicate with Apple activation servers. That doesn’t happen unless you put a SIM card from another carrier into the phone or do a backup/restore or erase your phone and set up as new.

OP started a new thread with some info not previously provided.  Closing this thread as a duplicate.