Hi,
I newly purchased AT&T Postpaid Iphone week before.
During the activation Instead of AT&T SIM Card by mistake i put TMobile SIM Card into it (Ultra Mobile SIM Card)
So my AT&T Phone got locked by TMobile carrier.
Now i am not able to use my AT&T SIM in AT&T Phone because its been locked my Sprint TMobile carrier.
Initially i worked with Apple support to identify the problem. They only confirmed that TMobile is the one who has to release the lock to use this phone with AT&T.
I have been working with TMobile for a week and did not get a proper response from them.
They initially said that they want to whitelist this IMEI so they sent a request to internal dept.
Then they asked me to go to physical TMobile store to verify my identity, Physical phone and Prrof of purchase --- I completed all these process
Still my phone is locked by TMobile and they are not responding properly.
Let me know what else i can do before TMobile unlock my phone.