The phone was probably reported as stolen and the IMEI was putted on the BLACKLIST by Tmobile. This is why a TMobile branded phone does not work on Tmobile network.

Samsung Galaxy T989 are very expensive phones and this is one of the few phones TMobile will disable the IMEI if reported lost or stolen. Buyers should be aware of buying such phones on Craigslist or Ebay.

 

My T-mobile T989 is unlocked, and works fine on T-mobile.

-WillieB

 

I'd go with leeintl for this one if someone stole the phone and tried selling it on eBay there is a good chance that the IMEI is burned and you cannot use it o T-Mobile. If you want to buy the phone under contract with T-Mobile after a month they will not have a problem giving you the unlock code I did it with my phone. If you however buy a locked phone and you want to unlocked without having a contact they will not provide the code I think.