Please help

I found an Iphone 4S - reported it to the local police who said if it is not claimed within one month then I can keep it. I reported to the Apple Iphone Store, tried to phone Apple who were not really helpful - i have really tried to trace the owner who obviously does not want the phone back. Now I would like to use it. How can i unlock the carrier locking? I dont know who the carrier is to request them to unlock the phone - Apple said that they could see who the phone belonged to and the carrier, but could not "divulge" this information to me. I asked them to send the owner a message and gave them my contact details but to no avail. Please help - I would like to use the phone as no one else seems to want it...