iphone 5 calling and recieving calls problem

bought an iphone 5 from a guy and just found out he got it from another guy and it might be stolen. had it for a couple months, worked perfectly fine untill the other day. it doesnt make/recieve calls or text anymore but provider still allow me to use their internet(t-mobile).booked an appointment with apple but scared theyre going to confiscate it. are they allowed to take my phone and whats wrong with the phone?

p.s when i bought the phone it was wrapped up in its box so it was brand new, wasnt touched therefore wasnt second hand.