Hey there! I'm sorry to hear you're having so many issues getting the phone unlocked! Have you verified that the IMEI is the same as the device you sent off? As in, is it possible Samsung replaced the phone instead of repairing it?
Device is same, IMEI is same. T-mobile customer care also confirmed device is same. Was able to pull Samsung and T-mobile guys on the phone together and T-mobile confirmed ONLY they can unlock the phone. They submitted lot of escalation tickets, expedited tickets and assured that they will bypass regular process of unlocking my device using DEVICE UNLOCK app and will get me an unlock code, They also assured call back to check if device unlock worked, no one has called back. Customer care also assured everytime that I'll not get email saying there is NO UNLOCK CODE and it has to be unlocked using DEVICE UNLOCK APP. However, everytime they submit the request I get same email that there is no unlock code and it can be unlocked using DEVICE UNLOCK app only.
I'm planning to share my experience on social media and take legal action against them if T-mobile doesnt solve the issue very soon.