One - "BC50" is not your phone's model but in FACT the battery... lol
Two - Subsidy unlock code is the code to unlock the phone to be able to be used with other GSM service providers. I'm gonna take it as the phone is not from the same company as yours. If it were, you could ask your service provider for it and they would give it to you for free. This will not work for you because the phone is not of your service provider. You will have to go get it unlocked either online or at a nearby storefront by your home that does cell phone unlocking. I would give a little bit more info if I knew exactly what model your Motorola was and not the battery.
What is Motorola Mobile Correct Model....You need to specify that..Because BC50 is battery type.You can get the subsidy code for Motorola Phone at Onlinegsmunlock.com/motorola/rs7wp8/ and Unlock it easily.