Why cell phone doesn't works in a closed elevator

For a cell phone to work, it must be able to recieve electromagnetic signals. When a cell phone is inside a closed elevator, the elevator acts as a Faraday cage. The electric field inside the elevator is ZERO . Hence cell phones are unable to recieve signals inside an elevator.

A hollow conductor or the conducting wire cage that shields its interior from external fields is called as Faraday cage or Faraday shield.