Find out original carrier

Hi guys. Is there a way to find out what the original carrier for a BB10 phone is?
I bought this Classic which was supposed to be unlocked but it isn't. There's no branding on the phone or box at all. I tested with several SIM cards and the only one it accepts is the T-Mobile one, but they said they can't find its IMEI in their system.
Any ideas?
Thanks!

Posted via CB10

If the only one it accepts is t-mobile...

Well, you can do the math.

Posted via -sigh- Priv. Guess we have to get used to Android guys....

Originally Posted by John Vieira

If the only one it accepts is t-mobile...

Well, you can do the math.

Posted via -sigh- Priv. Guess we have to get used to Android guys....

That's not necessarily true. I have this other phone which takes a Pure Talk SIM card but won't take one from T-Mobile or Verizon. Does that mean it's locked to Pure Talk? It's not.