 FACT: Det. Messer is on a train talking on a cellphone to Mac. He  hangs up by saying something like "Ill talk to you later, I think I  am going to loose the signal". The problem is he is in the subway  underground, you cannot get a cellphone signal once underground in  the NY subway system you can only get service if the train is on the  surface (above ground) this is true even if the train stops  partially underground. A few major cellphone companies are trying to  bring service to the subways but it has not happened yet.