A few suggestions on what to do while you are at the airport
Money changers are hard to find in Tokyo, except for banks which operate only 9:00-15:00 on weekdays. If you have foreign currency, you may be able to save time by exchanging it at the airport.
Some Japanese bank ATMs do not accept foreign credit cards. In that case you can try Seven Bank which is commonly found at a Seven Eleven convenience store.
Free WiFi is rare Japan. Airports have WiFi. Starbucks shops usually have free WiFi for guests, but you are required to register your email with them beforhand. See Basic Information for advance registration with Starbucks WiFi.
While public phones are disappearing from Japanese towns, they are easily found at airport terminals. Call with coins or a 'telephone card' sold at convenience stores such as Seven-Eleven, Family Mart or Lawson at the airport.
Get a copy of free subway map in English
You can get a free subway map in English at Narita Airport information desk.