If you inserted a new SIM card and now it is asking you for a PIN or unlock code to unlock it, that is not the end of the phone, there is a solution to that some of those Samsung phones that comes up with this issue are mostly from abroad either we bought it from someone or it was send to you from outside country.
Reasons why they are network lock are.
It is either the phone was bought from a carrier with payment to be completed, and later the phone was sent out of the country without the owner completing the payment for the phone to be unlocked to other network providers so the phone get to you without fully unlocked to be able to use other network.
Kindly slide in my DM for your service #08052486309