Revived Galaxy S3 asking for "SIM Network Unlock PIN"

[imaddicted2u]

I was given a broken Samsung Galaxy S3 SGH-I747M that was going to throw away. The thing was dead. I figured out how to Re-flash the stock firmware (Android 4.4.2) and that brought it back to life. Since there were Rogers and Fido account apps on the phone, I assumed that a Rogers SIM would be the way to go, so I picked one up in prep for setting up an account. Trouble is when I plug in the SIM, a LTE Micro SIM, and power up the phone it asks for a "SIM Network Unlock PIN". Since I don't have that code, what should I do next? Could it be that the LTE Micro Sim is not compatible with the Galaxy S3? If I dismiss the message the phone works fine but only on WIFI of course. I also checked the device IEMI number and it hasn't been reported lost or stolen and is not currently on the national blacklist. Thanks in advance.

***Edited Labels***

[Pauly]

Its possible the phone is SIM LOCKED to the Fido (302-370) network ID. You can go to a fido store and politely ask them to try a fido chip they should have no issue checking. Or its also possible the phone is locked to someone entirely different. Give it a try and let us know

[imaddicted2u · Accepted solution]

Thanks, solved. Turns out to be locked to Bell. I guess I'll have to get it unlocked to bring it to Rogers.