Ifound an iphone and went to my local police station to report the inccident after two weeks they gave me back the phone

I need to know if I can unlock this phone as I was told I could because nobody claimed, and they gave me tittle papers for as it being mine. I have those to submit to Apple but I need to know if this can be done without carrier interverntion because they want to enslave me with a two year contract even if the phone is my sole property.