Cellphones are not listed in the phone book nor is their a caller id system created for cell phones other than the contact list you save personally. When a strange number calls you and you want to know who it is before answering you now can use a unique form of phone number identification. Online there are a number of companies who have access to cell phone directories. You can do a reverse phone lookup to identify the caller, the location of the caller’s billing address and any other information the company might have on that number. You can see if it’s an old friend trying to reach you for a reunion or if it’s a telemarketer trying to sell you new dryer sheets.