This is an Apple user to user technical support forum.
It is not a forum for people to help you contact phone companies or carriers. You should have thought about this and asked these questions before you purchased the phone.
You need to speak to the friend who gave you the phone about this and ask for his help. If he gave you the phone, then he should be able to answer all your questions and point you in the direction of the carrier.
This does sound as if the phone could be stolen, so there is a chance that you will not ever be able to use the phone, especially if you come up against the activation lock on the phone and don't have the correct details. If you don't have these details then you own useless brick and will never be able to use this phone carrier locked or anything else.