My AT&T Apple Iphone 13 Pro Max is locked by TMobile

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.